Instructions

for the filling

 In large saucepan, bring raspberries, sugar, and lemon juice to boil over medium-high heat, stirring often. Boil until raspberries have broken down and released their juices, about 5 minutes.
 Whisk in chocolate until completely melted, about 1 minute. Continue to boil mixture, stirring and adjusting heat as needed, until jam has thickened and measures 1 cup, 10 to 15 minutes. Remove pot from heat. Transfer jam to bowl and let cool completely, about 1 hour.

for the cake

 Adjust oven rack to middle position and heat oven to 350 degrees. Grease 13 by 9-inch baking pan, line with parchment paper, and grease parchment.
 Process sugar and almond paste in food processor until mixture resembles coarse sand, 20 to 30 seconds. Add eggs, vanilla, baking powder, and salt and process until pale yellow and frothy, about 2 minutes. With processor running, slowly add melted butter in steady stream until incorporated, about 10 seconds. Add flour and pulse to combine, 4 or 5 pulses.
 Transfer 1⅔ cups batter to prepared pan and spread in even layer with offset spatula; set remaining batter aside. Bake until top is set and edges are just starting to brown, 8 to 10 minutes. Let cake cool in pan on wire rack for 5 minutes. Remove cake from pan, discarding parchment, and let cake cool completely on rack. Let pan cool slightly, about 10 minutes. Line now-empty and cooled pan with clean parchment paper, and grease parchment. Transfer 1⅔ cups batter to prepared pan and repeat baking cake and cooling pan. Repeat baking and cooling with remaining 1⅔ cups batter.
 Transfer one cooled cake layer, bottom side up, to cutting board. Spread ½ cup filling evenly over top, right to edge of cake. Top with second cake layer, bottom side up, and spread remaining ½ cup jam evenly over top. Top with third cake layer, bottom side up.

for the topping

Microwave white chocolate chips and bittersweet chocolate chips in separate bowls at 50 percent power, stirring occasionally, until melted, 2 to 4 minutes. Using small offset spatula, spread white chocolate evenly over top of cake, right to edges of cake. While white chocolate is still warm, use small spoon to drizzle dark chocolate crosswise in thin parallel lines over white chocolate. Gently run tines of fork lengthwise across top of cake to create delicate, webbed pattern. Let cool until chocolate has set, 1 to 2 hours.
 Dip serrated knife in very hot water and wipe dry before each cut. Trim away edges. Slice cake lengthwise into 5 equal strips (about 1½ inches wide), and then crosswise into 12 equal strips (about 1 inch wide). Serve. (Petit fours can be refrigerated for up to 24 hours.)