Tear the 6 croissants into 2-inch pieces and set aside. In a large bowl, whisk together the 4 eggs, 2 egg yolks, 1 cup sugar, 0.75 cup milk, 1.25 cups cream, 0.5 tsp almond essence, and 0.25 tsp vanilla extract until well combined and the sugar is fully dissolved. The egg yolks add richness and create a more velvety custard, so don't skip them. In a separate small bowl, combine 0.75 cup ground almonds and 1 tsp cinnamon, then set aside.

Grease a 9-inch round baking dish or similar size with butter or cooking spray. Layer half of the torn croissant pieces on the bottom of the pan, creating an even base. Sprinkle half of the almond-cinnamon mixture from Step 1 over the croissants, then scatter 1 cup of blackberries evenly across. Add the remaining croissant pieces as the second layer, then top with the rest of the almond-cinnamon mixture and the 1 cup of raspberries. I like to distribute the berries evenly so each slice gets plenty of fruit.

Pour the custard mixture from Step 1 slowly and evenly over the layered croissants and berries, ensuring it distributes throughout all the layers. Let the assembled cake sit at room temperature for 1 hour, allowing the croissant pieces to absorb the custard and soften slightly. This resting period is crucial—it transforms the bread into a tender, custard-soaked cake rather than a dry pastry.

Preheat your oven to 325°F. Top the soaked cake with 0.33 cup of slivered or sliced almonds, distributing them evenly across the surface for texture and visual appeal. Place the baking dish in the preheated oven and bake for 45–60 minutes, until the custard is set but still has a slight jiggle in the center and the almonds are golden brown. The baking time depends on your oven, so start checking around 45 minutes.

Remove the cake from the oven and let it cool in the pan for about 30 minutes—this allows the custard to set further and makes serving easier. Once cooled, dust the top generously with sifted powdered sugar for a professional, elegant finish. Serve warm or at room temperature, and know that this cake is even better the next day as the flavors meld together.