1. Preheat the oven to 350°F and line a baking sheet with parchment paper.

2. Mix the oats, flour, brown sugar, salt, and part of the melted butter until a soft oat cookie dough forms.

3. Press the dough onto the baking sheet and bake for 15 to 18 minutes, or until golden. Cool completely.

4. Crumble the cooled oat cookie into fine pieces and mix with remaining melted butter until the crumbs hold together.

5. Press the crumb mixture firmly into a 9-inch pie dish, covering the bottom and sides evenly.

6. In a bowl, whisk granulated sugar, brown sugar, powdered milk, cornstarch, and salt.

7. Add egg yolks, heavy cream, vanilla, and melted butter, then whisk gently until smooth.

8. Pour the filling into the prepared crust and bake for 30 to 35 minutes, until the edges are set and the center has a slight jiggle.

9. Cool the pie at room temperature, then refrigerate for at least 4 hours or overnight.

10. Dust with powdered sugar before slicing and serving chilled.