Step 1

In the bowl of a stand mixer fitted with a paddle attachment, beat the butter on low speed until smooth. Add the sugar, vanilla, and salt. Mix on low speed until well creamy and smooth. Add the flour and mix on low speed until just uniform in texture.

Step 2

Gather the dough into a ball, divide the ball into two, and flatten each portion into a disc. Wrap tightly and refrigerate for at least 3 hours. If you are running low on time, throw it in the freezer for about 30 minutes.

Step 3

Once the dough is chilled, take on of the discs and transfer it to a piece of parchment paper, cover with a second piece of parchment and flatten to form a rectangle about 1/4-inch thick.

Step 4

When ready to bake, preheat the oven to 350 degrees. Line a baking sheet with parchment paper. Cut the dough with cookie cutters of choice and place them on the lined baking sheet. These won’t spread too much, if at all. Repeat with second portion of dough. If cookie cut outs are starting to get soft by the time you have finished cutting out all the shapes, pop the baking sheet in the freezer for 10 - 15 minutes to allow the cut outs to firm up. A chilled dough will retain its shape better when baking.

Step 5

Bake until golden around the edges, approximately 10 - 12 minutes. Remove pan from the oven and allow the cookies to cool on baking sheet for at least 10 minutes before transferring them to a wire rack to cool completely.

Step 6

Make the shortbread dough recipe as listed above.  When rolling out the chilled shortbread dough, roll the dough to just a bit thinner than 1/4-inch thickness. With the larger square cookie cutter, cut out as many large squares as you can and transfer the square cut outs to a lined baking sheet. With the smaller square cookie cutter, punch out a square in the centre of each larger square. It is important that you make the smaller square cut out once the larger square has been transferred to the cookie sheet, or else the cookie will lose its shape when you try to transfer it. Gather the smaller square cut outs that you have removed from the larger square. Re-roll that dough and repeat the previous steps until all the cookie dough has been used up. If the dough starts to get soft, chill the dough again before cutting out the shapes.

Step 7

Bake the squares for 6 - 7 minutes, until the edges of the cookies are golden. Keep a close eye on the cookies at the 5 minute mark because the cookies are thin and will start browning really quickly. Remove the cookies from the oven and allow them to cool completely on the baking sheet before handling. They will be very delicate. Transfer the cookies onto another baking sheet lined with a clean piece of parchment. We will be pouring the isomalt on this surface.

Step 8

Top cookie which will be filled with isomalt and decorated

Step 9

Middle cookie to 'raise' the cookie so the sprinkles can move freely inside the cookie

Step 10

Bottom cookie which will be filled with isomalt

Step 11

Preheat oven to 265F.

Step 12

Place the isomalt crystals in a small pot over medium heat and allow the isomalt crystals to melt without stirring them. Once the isomalt is boiling, remove the small pot from heat. Isomalt will be very bubbly. Hold the small pot off of the heat until the bubbles settle down.

Step 13

Once the bubbles have settled down, place the pot back down on the burner and stir in the water, a little at a time. Steam will aggressively come off of the sugar as the water is now cooling it down. Isomalt will still be very bubbly.

Step 14

Reduce the amount of air bubbles in the hot isomalt by placing it in the oven at 265F for 10 minutes. If you skip this step, the bubbles will stay in the isomalt and will harden with the bubbles still visible.  After 10 minutes, carefully remove pot of isomalt from oven and use the isomalt while it is still hot. Carefully pour the hot isomalt into the centres of each cookie cut out and spread the isomalt to the edges and corners of each cookie with a small spoon. If the isomalt starts to thicken, place it back in the oven for 2 - 3 minutes until it liquefies again. Allow the isomalt to cool completely before moving the cookies, at least 10 minutes

Step 15

Once the isomalt has set, take a piece of paper towel and dab it in a small dish of oil (I use vegetable oil). Gently polish the back side of the isomalt (the side that was on the sheet tray). This will make the isomalt extra clear and see through.

Step 16

Place one isomalt-filled cookie down. Apply royal icing to the edges of the cookie, being cautious to not get any icing on the 'glass.' Stack the hollow cookie before the royal icing dries. Fill your cookie with sprinkles of choice. Attach last isomalt-filled cookie with royal icing to 'seal' the cookie. Decorate the top of each cookie.

Step 17

In a medium bowl, whisk together flour, baking powder, baking soda, and salt. Set aside.

Step 18

In a bowl of a stand mixer, beat together butter and sugars until creamy and smooth. Add egg yolk and vanilla and beat until combined. Add the dry ingredients in two increments and mix until just combined. Chill the dough, covered, for at least one hour.

Step 19

When dough has been chilled, portion dough into 14 equally-sized dough balls. Dip each ball into egg white before rolling in sesame seeds to cover the entire ball. Transfer covered dough balls to a lined baking sheet, placed 2 inches apart.

Step 20

Bake dough balls at 325F for 12 - 15 minutes until the edges are a light golden brown and the centres are just set. Allow cookies to cool on baking sheet for ten minutes before transferring them to a wire rack to cool completely.