In a large bowl mix 4 cups blackberries
3/4 cup sugar
1 tbsp flour
1 tsp lemon rind
Mix together and set aside.
Take thawed but cold puff pastry (I used the thawed frozen kind). Roll out on floured serface. I rolled out until I had enough for 3-4 layers of pastry.
Beat one egg with a little water and brush on both sides of pastry.
In a lightly greased square or rectanguar baking pan, pour in the berries. Lay down layer after layer of pastry brushed with egg.
Bake at 375 for 30-40 minutes.