Preheat the oven to 325ºF. Grease the bottoms of two 9-inch cake pans or line the bottoms of the cake pans with parchment paper. Leave the sides of the cake pans ungreased.
Beat the egg yolks:
Add the egg yolks to a large mixing bowl and beat with an electric mixer until pale and thick; they will increase in volume. This takes about 5 minutes of consistent mixing.
Add 1 cup (200g) sugar, 2 tablespoons at a time, mixing well after each addition. Add ¼ cup (60ml) whole milk and beat until smooth.
Sift the flour and baking powder into the egg yolks and beat until just combined.
Prepare the egg whites:
Beat the egg whites until medium-stiff peaks form.
Finish the batter:
Fold the egg whites into the batter and stir gently until combined and no white streaks remain.
Bake the sponge cakes:
Pour the batter into the prepared cake pans. Transfer to the oven for 25 to 30 minutes or until the sponge cakes are firm to the touch and a toothpick inserted into the center comes out clean.
Cool the sponge cakes:
Remove the sponge cakes from the oven and let them cool for 5 minutes. Use a butter knife or a thin spatula to run around the sides and bottom of the pan to separate the cake from the pan.
Flip the pan over onto a wire rack or onto large plates and lightly tap the bottom of the pan to release the cake if needed. You’re going to be cutting it up into bite-sized pieces, so don’t fret if it doesn’t come out perfectly!
Allow the sponge cakes to cool for at least 1 hour. Once cool, you can wrap them in plastic wrap until you’re ready to begin the trifle.
Prepare the streusel:
Preheat the oven to 375ºF.
Place 1 cup (125g) pistachios in a gallon storage bag and use a mallet or heavy-bottomed pan to crush them. To the bag, add 3 tablespoons (40g) butter, 3 tablespoons (25g) flour, 2 tablespoons (25g) brown sugar, 1 tablespoon (21g) honey, and a pinch of salt. Close the bag and use your hands to combine all of the ingredients.
Pour the mixture onto a baking sheet. Transfer to the oven for 6 to 8 minutes. Use a spatula or flipper to gently flip and loosen up the streusel midway through baking. Remove the baking sheet from the oven and transfer the streusel to a bowl. Allow the pistachios to cool completely before assembling the trifle.
Make the whipped cream:
Combine 1½ cups (360g) heavy cream, ½ cup (60g) powdered sugar, and 1 teaspoon vanilla extract in a large bowl. Beat with an electric mixer until stiff peaks form. Transfer to the refrigerator.
Prepare the pudding:
Combine the contents of the pudding envelopes and the whole milk in a large bowl. Whisk for 2 minutes until soft-set. Transfer to the refrigerator for 10 minutes to thicken.
Assemble the trifle:
Cut the sponge cake into bite-sized cubes.
Arrange half the cubes on the bottom of a trifle bowl. Press them together lightly to create a tight layer. Add half the pistachio pudding and use a rubber spatula to gently smooth it out into an even layer. Be careful not to break up too much of the sponge cake. Next, add half the whipped cream and gently smooth it out.
Add the remaining sponge cake cubes and top with the remaining pudding. Finish with the remaining whipped cream. Top the trifle with all of the pistachio streusel.
Transfer the trifle to the refrigerator for at least 1 hour up to 24 hours. The whipped cream is stabilized with the powdered sugar, but it’s best eaten within 24 to 48 hours.
To serve:
Remove the trifle from the refrigerator and top with a few mint leaves if desired. Enjoy!