Prepare pastry:
Preheat oven to 425°F.
Unfold pastry sheet, then turn over (to prevent creases
from splitting during baking). Cut 6 (4 1/2-inch)
triangles from sheet with a long sharp knife and a ruler.
Arrange triangles on a greased baking sheet and lightly
prick centers a few times with a fork. Bake in middle of
oven until puffed and golden brown, 15 to 18 minutes.
Transfer to a rack and cool.
Make purée while pastry bakes:
Stir together cornstarch, water, and lemon juice in a
small saucepan. Add berries and sugar and simmer over
moderately high heat, stirring and breaking up berries,
until thickened, 3 to 4 minutes. Force purée through a
fine sieve into a bowl, pressing hard on solids, then cool
purée at room temperature.
Make cream:
Boil wine in another small saucepan until reduced to about
1 tablespoon, 10 to 12 minutes, then cool.
Beat cream with confectioners sugar and zest in a bowl
until it just holds stiff peaks. Fold wine into cream
until just incorporated, then chill.
Split each pastry triangle in half horizontally and
make a sandwich with about 1 1/2 tablespoons cream. Spread
1 teaspoon purée on top of each pastry, leaving a
1/4-inch border (there will be purée left over).
Decoratively arrange some raspberries and blackberries on
top and sift some confectioners sugar over berries.
Cooks' notes:
• Berry purée can be made 2 days ahead and chilled,
covered.
• Orange Muscat cream can be made 8 hours ahead and
chilled, covered.
