Set out frozen puff pastry for 30-40 minutes until it is easy to unfold, but still cold. If it gets warm and sticky, put in the freezer for 5 minutes or in the refrigerator for 10-15 until chilled again.
Preheat oven to 400 degrees. Mix together pumpkin, brown sugar, maple, and pumpkin spice in a medium mixing bowl.
Remove parchment wrapping and unfold pastry. Gently roll out with a rolling pin to flatten the edges.
With a pizza cutter, cut 1-inch strips down the left and right thirds of the pastry dough, leaving the center untouched.
Fill the middle with the pumpkin filling to desired amount.
Take the first strip on the right and lay it across the filling, repeat with the first strip on the left. Continue right to left all the way down the pastry.
Mix the egg with the water to make an egg wash. Gently brush the pastry with the egg wash (this will help it brown to the pretty golden color).
Bake at 400 degrees for about 20 minutes until golden brown and puffed up.
Let the pastry cool for 10-20 minutes while making the glaze.
To make the glaze, mix the sugar, maple, butter, and milk. Add more maple for a stronger flavor, and more milk (in small increments) until you get the desired consistency.
When the pastry is warm but not hot, drizzle the glaze over in gentle sawing motions.