Step 1

Preheat oven to 350 degrees F. Lightly butter a 9-by-5-inch loaf pan and line with a 9-inch strip of parchment paper (the two short ends will be uncovered); lightly butter parchment.

Step 2

Melt butter in a medium saucepan. Remove from heat and add chopped chocolate, stirring until smooth (the residual heat from the pan should be plenty to melt the chocolate.)

Step 3

Stir in sugar; mixture should be lukewarm, no longer hot to the touch. If it's still pretty warm, let it cool for a minute or two.

Step 4

Whisk in eggs until batter is smooth and shiny.

Step 5

Sift together flour, cocoa powder, baking powder and salt in a small bowl. Sprinkle over chocolate mixture and fold with a spatula until just incorporated.

Step 6

Pour batter into prepared pan and spread into an even layer. Bake for about 20 minutes or until top is set and a toothpick inserted near the middle comes out with moist crumbs (not gooey batter). Set pan on a wire rack and let cool completely. The brownie layer can be made a day ahead of time; once cool, cover pan tightly and refrigerate overnight until ready to use.

Step 7

Lift the cooled brownie out of the pan using the parchment overhang as handles. Cut off the edges, then cut into six 2-inch squares. The scraps and the sixth square make a lovely chef's snack. ;)

Step 8

Place water in a small dish; sprinkle gelatin over top and set aside to bloom for at least 5 minutes.

Step 9

Heat milk in a small saucepan set over low heat until it just starts to steam (try not to let it boil).

Step 10

Mix together egg yolk and sugar in a bowl until it forms a thick paste. Slowly spoon some of the hot milk into the yolk mixture, whisking constantly until the paste thins out a bit. Drizzle in the remaining milk and whisk until smooth.

Step 11

Return mixture to the saucepan and return to low heat and cook, stirring and scraping the bottom of the pan consistently, until the mixture thickens slightly to coat the back of a spoon (it should measure about 175 degrees F on an instant read thermometer.

Step 12

Remove from heat and whisk in gelatin until smooth. Transfer to a medium-large bowl and set aside.

Step 13

Meanwhile, purée strawberries and lemon juice in a blender or food processor until smooth. Transfer to a liquid measuring cup (you should have about 1/2 cup purée, if you have more than that save the excess for another use). Whisk strawberry purée into lukewarm custard mixture, then place bowl in refrigerator while you whip the cream.

Step 14

In a clean bowl or the bowl of a stand mixer, beat heavy cream until it holds soft peaks. Add 1/3 of cream to the cooled strawberry mixture and fold to lighten, then add remaining cream and fold until fully incorporated and no white streaks or lumps remain.

Step 15

To assemble your cakes, spoon or pipe the mousse into silicone molds, about 2/3 of the way full. Gently press a brownie square into the top of each mousse-filled mold. Scrape with an offset spatula to make the top perfectly level with the top of the mold. Freeze at least 3 hours or overnight until completely firm.

Step 16

Before you make the glaze, remove cakes from molds and place on a frozen cookie sheet lined with parchment paper. Return to freezer until just before glazing.

Step 17

Place chopped chocolate in a medium-sized, heat-proof bowl and set aside.

Step 18

Heat cream and corn syrup in a small saucepan until it just starts to bubble (do not let it boil).

Step 19

Pour over chopped chocolate and let sit for 30 seconds, then gently whisk, starting in the center and moving in gentle concentric circles until an emulsion forms, then working your way out to the edges until the entire mixture is smooth and emulsified.

Step 20

Remove cakes from freezer and place on a cookie sheet, elevated off the sheet using small jars or cookie cutters (ideally something smaller in diameter than the cake itself so the glaze can drip off). You may also want to cut out small rounds of parchment to place under each cake to make them easier to transfer.

Step 21

Pour glaze generously over cakes, taking care to ensure there are no bare spots left. Gently scrape the edges to remove any remaining drops, then carefully transfer cakes using a small 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 another use.

Step 22

Glazed cakes will keep in the refrigerator for up to 3 days. Let come to room temperature before serving.