Prepare Pistachio Butter: Use store-bought or homemade pistachio butter.
Beat Egg Whites: In a bowl, beat egg whites with 1/4 cup sugar until stiff peaks form.
Whip Egg Yolks: In another bowl, whip egg yolks with remaining 1/4 cup sugar until pale and fluffy.
Mix Cream: Add mascarpone, pistachio butter, vanilla, and almond extracts to yolk mixture. Beat until smooth.
Fold: Gently fold egg whites into mascarpone mixture to keep it light and airy.
Dip Ladyfingers: Quickly dip ladyfingers in cooled coffee (with amaretto if using).
Layer: Arrange half of the ladyfingers in a 9x9-inch pan. Spread half of the cream mixture on top. Repeat layers.
Chill: Cover and refrigerate for at least 6 hours or overnight.
Serve: Before serving, sprinkle with chopped toasted pistachios. Slice and enjoy!