For Caramel Sauce:Combine sugar, corn syrup, and 1 tablespoon water in a small, high-sided saucepan set over medium-high heat. Bring to a simmer, brushing down any stray sugar crystals from the side of the pan using a wet pastry brush. Stop stirring once sugar has dissolved and mixture comes to a boil.Continue to boil, swirling the pan occasionally to ensure even cooking, until the sugar darkens to a rich amber color.Add the butter and whisk until completely melted and smooth.Remove from heat and add the heavy cream. It will bubble violently and may appear to seize up; continue to stir until smooth and uniform. Once it’s smooth again, return to medium heat and boil until it reaches 230 to 235 degrees F.Let cool for 5 minutes or so, then add caramelized white chocolate, stirring until melted and smooth. Let cool to room temperature before layering onto frozen cremeux. Or, if you want to store and use it later, transfer to a jar or heat-proof container, then cover and refrigerate up to 7 days until ready to use. You may need to reheat it in the microwave or stovetop until it’s pourable.For Chocolate Crémeux:Bloom gelatin. For leaf gelatin, cut into strips and place in a bowl with cold water for at least 5 minutes to soften. For powdered gelatin, sprinkle over 1 tablespoon of cold water and let sit for at least 5 minutes.Gently melt chocolate in a double boiler or a heat-proof bowl set over, but not touching, an inch or so of gently simmering water. Remove from heat and set aside.Combine milk and cream in a small saucepan. Heat over medium until steaming and just barely starting to bubble.Whisk egg yolk in a small bowl. Slowly whisk in 1/4 cup of hot milk mixture into egg yolk, whisking constantly. Continue to whisk in a bit more hot liquid at a time until egg mixture is hot to the touch. Add back to saucepan with remaining milk and return to medium heat.Cook, stirring constantly and scraping the bottom and sides of the pan as you go, until mixture thickens (it should read 170 degrees F on an instant read thermometer). Remove from heat.If using leaf gelatin, wring out as much water as possible. For powdered gelatin, microwave for 5 to 10 seconds and stir until melted. Add gelatin to hot milk mixture in the saucepan, whisking until well combined.Add melted chocolate and stir until completely incorporated.Spoon mixture into silicone molds (approximately 1 3/4-inches in diameter), leaving about 1/4-inch of room at the top of each mold (if you are skipping the caramel layer, you can fill the molds to the top). Place mold on a flat surface like a sheet pan, and place in the freezer, making sure the mold sits level. Freeze until firm, at least 4 hours.Once cremeux is completely set, pour caramel on top, filling just to the top of the mold. Return to freezer and freeze overnight until firm. Reserve remaining caramel for the mousse.For Chocolate Pecan Crust:Preheat oven to 350 degrees F. Line an 8-by-8-inch baking pan with parchment paper.In a food processor, pulse pecans until finely ground (don’t go so far as to make pecan butter; a coarse crumb is fine).Add flour, sugar, cocoa powder and salt and pulse until evenly distributed.Sprinkle butter cubes over dry ingredients. Pulse until butter mixture forms coarse, dry crumbs. Pinch a bit of the mixture together between your fingers; if it sticks together, it’s good to go. If not, sprinkle over a teaspoon or two of milk and pulse until evenly incorporated.Dump crumb mixture into prepared baking pan, and press into an even layer over the bottom of the pan.Bake for 15 to 18 minutes or until set. Let cool slightly, then cut out 5 rounds (use a cookie cutter that is about 1/2 smaller overall than your silicone mold). It’s easier to cut cleanly while the crust is still warm.Place pan on a wire rack and let cool completely (ideally overnight to let it dry out and get crunchier). Use an offset spatula to transfer rounds to a baking sheet, then place in freezer until ready to use.For Caramel Mousse:Bloom gelatin. For leaf gelatin, cut into strips and place in a bowl with cold water for at least 5 minutes to soften. For powdered gelatin, sprinkle over 1 tablespoon of cold water and let sit for at least 5 minutes.Combine caramel and milk together in a small saucepan. Heat over medium until steaming and just starting to bubble.Whisk egg yolk in a small bowl. Slowly whisk in 1/4 cup of hot milk mixture into egg yolk, whisking constantly. Continue to whisk in a bit more hot liquid at a time until egg mixture is hot to the touch. Add back to saucepan with remaining milk and return to medium heat.Cook, stirring constantly and scraping the bottom and sides of the pan as you go, until mixture thickens (it should read 170 degrees F on an instant read thermometer). Remove from heat.If using leaf gelatin, wring out as much water as possible. For powdered gelatin, microwave for 5 to 10 seconds and stir until melted. Add gelatin to hot milk mixture in the saucepan, whisking until well combined.Add white chocolate and stir until completely incorporated. Transfer to a large, heat-proof bowl and let cool completely, stirring occasionally, to about 85 degrees F.Once caramel mixture is cool, whip cream using the whisk attachment on a stand mixer until it forms medium-stiff peaks.Spoon about 1/3 of whipped cream into bowl with caramel mixture, folding to lighten. Add remaining cream and fold until completely incorporated.Spoon mixture into 6 3-inch-diameter silicone molds, filling the molds about 2/3 of the way full. Place mold on a flat surface like a sheet pan to keep the mold level.Remove frozen crust rounds and cremeux domes from the freezer. Run a pairing knife around the top edge of the caramel layer to release it from the silcione, then press out the frozen domes. Carefully place one dome, caramel side up, into the center of each mousse-filled mold.Place a crust round directly on top of the caramel, and press until the crust is level with the top of the silicone mold. You may have some excess mousse that squeezes out, that’s ok. If you underfilled your molds, you might want to put a bit of mousse in a piping bag to fill it in as needed. Scrape off the excess mousse using an offset spatula.Place entire tray in the freezer, making sure the mold sits level. Freeze overnight until completely solid.For Mirror Glaze:Cut gelatin into 1-inch strips and submerge in cool water for at least 5 minutes to soften. Place white chocolate in a heat-proof bowl and set aside.Combine sugar, corn syrup, and water in a saucepan and bring to a boil over medium heat until sugar is completely dissolved and mixture is clear.Remove from heat and add gelatin (squeeze out as much water as possible first) and whisk until completely dissolved. Whisk in sweetened condensed milk. Pour hot mixture over chopped white chocolate and let sit for 30 seconds, then stir until chocolate is completely melted and mixture is smooth (you can also use an immersion blender if you have one to expedite this process, just try not to mix air bubbles into the glaze if possible).Let glaze cool, stirring occasionally, until glaze reaches approximately 90-94 degrees F on an instant-read thermometer. The glaze needs to be the correct temperature or it will not form a thick enough layer on the outside of the cakes.When the glaze reaches 95-96 degrees, add powder or gel food coloring as desired (I used a generous amount of Americolor Super Red, you need quite a bit more than you think you will to get an ultra rich color). If at any point your glaze gets too cool/thick, microwave it in 10 second bursts, stirring to even out the temperature throughout.If you want to make the glaze ahead of time, store it tightly covered in the refrigerator until you’re ready to use it. Before glazing, rewarm the glaze in the microwave in 30 second bursts, stirring well after each interval, until glaze is once again smooth and fluid. It’ll likely be warming than your target temperature of 94 degrees, so let it cool, stirring occasionally, until it cools down again to the appropriate temperature.Unmold frozen mousse cakes and place on a wire rack set inside a rimmed baking sheet to catch any excess glaze. Pour glaze generously over cakes. If your glaze seems a bit thin, you can do another layer, or let the glaze cool down a few more degrees which should give you a thicker layer. Allow the excess glaze to drip off for 5 or 10 minutes, then gently scrape the edges to remove any remaining drops. Carefully transfer cakes using an offset spatula to cardboard cake rounds or small pieces of cardboard for easy movement. Any leftover glaze can be scraped up and refrigerated in an airtight container for later use.To finish, press a gold-dusted Rolo into the side of each cake. Optionally, dip a paintbrush just barely into gold luster dust. Tap the brush with your finger over top of cakes to sprinkle a tiny bit of gold over the top of each cake.Glazed cakes will keep uncovered in the refrigerator for up to 5 days. Let come to room temperature 15 to 20 minutes before serving.