Step 1: Preheat your oven to 400°F (200°C). Place the unbaked pie crust into a 9-inch pie plate. Crimp the edges as desired.
Step 2: Prick the bottom and sides of the pie crust several times with a fork. You can blind bake for 10-12 minutes if desired, then cool slightly.
Step 3: In a medium bowl, whisk together the all-purpose flour, granulated sugar, and light brown sugar until well combined and lump-free.
Step 4: Pour the melted butter into the sugar-flour mixture. Stir well with a spoon or whisk until a crumbly mixture forms.
Step 5: Gradually add the milk (or water) and vanilla extract to the mixture. Whisk until the filling is smooth and all ingredients are fully incorporated.
Step 6: Carefully pour the liquid filling into the prepared pie crust.
Step 7: Bake at 400°F (200°C) for 15 minutes.
Step 8: Reduce the oven temperature to 350°F (175°C) and continue baking for an additional 35-45 minutes, or until the pie's center is mostly set with a slight jiggle.
Step 9: Remove the Hillbilly Pie Poor Mans Pie from the oven and let it cool completely on a wire rack for at least 2-3 hours, or until fully set, before slicing and serving.
Step 10: Store any leftover pie loosely covered at room temperature for up to 1 day, or refrigerated for up to 3-4 days.