Step 1: Prepare the Cake Base. If making homemade sponge cake, bake and allow it to cool completely. If using store-bought ladyfingers, you can skip this step. Cut the cake or ladyfingers into approximately 1-inch thick slices or cubes.
Step 2: Make the Custard. In a medium saucepan, whisk together egg yolks, 3/4 cup sugar, cornstarch, and a pinch of salt. Gradually whisk in the milk and 1 cup heavy cream. Cook over medium heat, stirring constantly, until the custard thickens enough to coat the back of a spoon (about 8-10 minutes). Remove from heat, stir in 1 teaspoon vanilla extract and 1 teaspoon almond extract. Pour into a bowl, cover the surface with plastic wrap to prevent a skin from forming, and chill completely in the refrigerator (at least 2 hours, or overnight).
Step 3: Prepare the Raspberries. Gently wash the fresh raspberries and pat them dry. If using frozen, thaw and drain well. You can lightly sweeten about half of the raspberries with a tablespoon or two of sugar, depending on their tartness, and gently mash them to create a saucier layer. Leave the other half whole for vibrant visual appeal.
Step 4: Toast the Almonds. Spread the sliced almonds in a single layer on a baking sheet. Toast in a preheated oven at 350°F (175°C) for 5-7 minutes, or until lightly golden and fragrant. Watch them carefully as they can burn quickly. Let them cool completely.
Step 5: Whip the Cream. In a large bowl, using an electric mixer, whip the 2 cups cold heavy cream, powdered sugar, and 1/2 teaspoon almond extract until stiff peaks form. Be careful not to over-whip, or it may become grainy.
Step 6: Assemble the Trifle. Choose a clear glass trifle bowl or a large glass bowl to showcase the layers. Begin with a layer of cake pieces at the bottom, fitting them snugly to cover the base.
Step 7: Add Raspberry and Custard Layers. Spoon about half of the mashed or whole raspberries over the cake layer. Then, gently spread about one-third of the chilled custard over the raspberries.
Step 8: Layer with Whipped Cream and Almonds. Spread one-third of the whipped cream over the custard, then sprinkle with a portion of the toasted sliced almonds.
Step 9: Repeat Layers. Repeat the cake, raspberry, custard, whipped cream, and almond layers, finishing with a final layer of whipped cream, artfully dolloped or spread smooth, and garnish generously with the remaining fresh raspberries and toasted sliced almonds.
Step 10: Chill and Serve. Cover the trifle loosely with plastic wrap and refrigerate for at least 4 hours, or preferably overnight. This allows the flavors to meld and the cake to absorb the moisture from the custard and berries, creating a truly decadent dessert.