Rainbow Cookies

Preheat oven to 175°C (350°F) with the rack in the middle position. Line a 22x33cm (9x13 inch) rimmed jelly roll pan with parchment paper, leaving a 5cm (2 inch) overhang on the two long sides to easily lift baked layers later. In a dry stand mixer bowl fitted with a paddle attachment, beat 226g room-temperature almond paste, 226g softened unsalted butter, and 200g granulated sugar on medium speed for 4 minutes until completely smooth, pale, and free of almond paste lumps. Add 4 room-temperature egg yolks one at a time, beating 30 seconds after each addition, then stir in 1 tsp almond extract and 1/4 tsp fine sea salt. Turn mixer to low speed, gradually add 120g sifted all-purpose flour, and mix only until no dry flour streaks remain. In a separate grease-free glass bowl, whip 4 egg whites on medium-high speed for 2 minutes until stiff, glossy peaks form, then gently fold into the batter in three even portions to keep the mixture light and airy.

Divide the finished batter evenly into three separate bowls (roughly 320g / 1.3 cups per bowl). Leave one bowl uncolored (pale off-white), stir 1/4 tsp green gel food coloring into the second bowl until evenly tinted a soft pastel green, and stir 1/4 tsp red gel food coloring into the third bowl until evenly tinted a soft pastel red. Wash and dry the parchment-lined pan between each layer: spread the green batter in an ultra-thin, even layer across the entire pan bottom, bake for 8-9 minutes until the top is just set and edges are lightly golden, then lift out using the parchment overhang and transfer to a wire rack to cool completely. Repeat the baking process with the uncolored white batter, then the red batter, baking each layer 8-9 minutes at 175°C (350°F) and cooling fully on racks for 20 minutes before assembly.

Once all three cookie layers are fully cooled, heat 180g seedless apricot jam in a small saucepan over low heat for 2 minutes until runny, then pour through a fine-mesh sieve to remove any fruit lumps. Place the cooled green cookie layer on a flat cutting board, spread half of the warm strained jam evenly across the entire surface using a small offset spatula, leaving a 3mm (1/8 inch) border from the edge. Carefully align the white cookie layer directly on top of the jam-coated green layer, press gently to adhere, then spread the remaining half of the apricot jam evenly across the top of the white layer. Top with the red cookie layer, press gently to create a tight, even stack, then wrap the entire stack tightly in plastic wrap. Place a second 22x33cm (9x13 inch) pan on top of the wrapped stack, set two 450g (1 lb) canned goods or baking weights on the upper pan, and chill in the refrigerator for 1 hour to set the layers and fuse them together.

After the cookie stack has chilled for 1 hour and set, unwrap the plastic and trim any uneven edges from the stack with a sharp serrated knife to create a perfect, even rectangle. Place 170g chopped 70% dark chocolate and 1 tsp neutral vegetable oil in a dry heatproof bowl set over a small saucepan of gently simmering water (double boiler, ensure the bowl does not touch the water surface). Stir continuously over medium-low heat for 3-4 minutes until the chocolate is completely smooth and melted, reaching a temperature of 32°C (90°F) on a candy thermometer, then remove the bowl from the heat.

Pour half of the melted dark chocolate evenly over the top of the chilled red cookie layer, spread into a thin, even coat with an offset spatula, covering the entire top surface. Return the chocolate-topped stack to the refrigerator for 15 minutes until the top chocolate layer is fully firm to the touch. Remove from the fridge, flip the entire stack over so the uncoated green layer is facing up, pour the remaining melted chocolate over the surface, spread into a thin even coat, then use the tines of a fork to create light, wavy decorative lines across the wet chocolate if desired. Chill for another 20 minutes until the second chocolate layer is completely set.

Once both chocolate layers are fully set, remove the stack from the refrigerator and let it rest at room temperature for 10 minutes to prevent the chocolate from cracking when cutting. Use a sharp, thin-bladed knife warmed under hot running water and dried between cuts to slice the stack into 5cm (2 inch) wide strips, then cut each strip crosswise into 5cm (2 inch) square cookies, wiping the knife clean after every 2-3 cuts for sharp, clean edges. Arrange finished cookies on a serving platter, or store in an airtight container in the fridge for up to 1 week.