Preheat your oven to 375°F (190°C). Line a large circular or rectangular baking sheet with parchment paper to prevent the dough from sticking and to make cleanup easier.
In a medium mixing bowl, combine the pumpkin puree, brown sugar, pumpkin pie spice, and vanilla extract. Stir well until the mixture is smooth and the sugar is fully incorporated.
Unroll both tubes of crescent dough and separate them into triangles. Arrange the triangles in a circle on the prepared baking sheet. Place the wide ends of the triangles so they overlap slightly in the center, forming a ring, with the pointed ends facing outward. You should have a hole in the middle, looking like a sunburst.
Spoon the pumpkin mixture evenly onto the wide part of the dough triangles, creating a continuous ring of filling. If you are using pecans, sprinkle them evenly over the top of the pumpkin mixture.
Take the pointed end of each triangle and fold it over the filling toward the center of the ring. Tuck the points under the inner edge of the dough to secure the wreath shape. Some of the filling will show through the gaps, which creates a beautiful effect.
Whisk the egg with a teaspoon of water and lightly brush it over the dough. This will give your wreath a beautiful golden shine. Place the baking sheet in the oven and bake for 15 to 20 minutes, or until the pastry is puffed and golden brown.
While the wreath cools slightly, whisk together the powdered sugar and milk in a small bowl until smooth. Drizzle the glaze over the warm wreath before serving.