In a small bowl, stir together the espresso and granulated sugar until the sugar is dissolved. Stir in 1/4 cup water and the coffee liqueur.
Using an electric mixer with the whisk attachment, combine the mascarpone, confectioners sugar and vanilla at low speed. With the machine on, gradually pour in the cream, then turn the mixer up to medium speed and whip until thick and billowy but not stiff.
Invert the angel food cake onto a work surface. Using a large serrated knife, trim the brown crust off the top of the cake, then slice the cake horizontally into 3 layers. Place the widest layer cut side up in the bottom of a 7-inch-wide trifle bowl. Drizzle 1/4 cup of the coffee syrup evenly over the cake, then spoon 2 cups of the mascarpone mixture evenly on top. Finely grate one third of the white chocolate over the mascarpone. Repeat with the remaining ingredients to make 2 more layers. Cover the trifle and refrigerate for at least 4 hours or up to 2 days.