Milk Chocolate and Salted Caramel Gâteau Saint-Honoré

Preheat oven to 375 °F. Line 2 baking sheets with parchment paper. Unfold 1 puff pastry sheet on a lightly floured surface. Unfold second pastry sheet and place directly on top of first, forming 2 layers. Press slightly to adhere. Using a 10" cake pan or tart pan bottom as a guide, cut pastry with a paring knife into a 10" round. Place on 1 prepared sheet. Bake base until puffed and deep golden brown, about 30 minutes. Let cool. DO AHEAD:Can be made 1 day ahead. Store airtight at room temperature. For cream puffs, preheat oven to 375 °F. Combine milk, butter, sugar, and salt in a medium saucepan; bring to a boil. Remove from heat and add 1 cup flour. Stir to combine. Return to medium-high heat; stir dough vigorously until a dry film forms on bottom and sides of pan, about 2 minutes. Transfer dough to a stand mixer fitted with a paddle attachment. Add eggs one at a time, incorporating fully between additions. Scrape dough into a pastry bag fitted with a 1/2" tip or a plastic bag with 1/2" cut diagonally from 1 corner. Pipe 1"-1 1/4"-diameter rounds onto second parchment-lined sheet (there should be 25-30 rounds). Smooth any pointed tips with damp fingertips to form rounded tops. Bake for 20 minutes. Lower temperature to 325 °F and bake until golden brown and dry, 15-20 minutes. Let cool completely. Using a sharp knife, cut a small hole in bottom of each puff. DO AHEAD:> Can be made 2 months ahead. Store airtight in freezer. Thaw before continuing.