Preheat Oven:
Preheat oven to 350°F (175°C). Grease a 9-inch pie pan or line with parchment paper.
Make the Crust:
In a medium bowl, combine oats, flour, baking soda, and salt. Stir in melted butter and sugar until evenly combined. Press mixture firmly into the bottom and up the sides of the prepared pie pan. Bake for 10–12 minutes, until lightly golden. Remove and let cool slightly.
Prepare the Filling:
In a large bowl, whisk together brown sugar, melted butter, and heavy cream until smooth. Beat in eggs one at a time, then add salt, vanilla extract, and powdered sugar until well combined.
Assemble Pie:
Pour filling into the baked crust and smooth the top with a spatula.
Bake Pie:
Bake for 35–40 minutes, or until the center is set but still slightly jiggly. Cool completely at room temperature for 1–2 hours.
Chill and Serve:
Chill in the refrigerator for at least 1 hour before slicing for clean pieces. Serve as-is or with a dollop of whipped cream.