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

In a large bowl, cream together the butter, oil, granulated sugar, and powdered sugar until smooth. Add the egg and vanilla extract, mixing until combined.

Stir in the flour, salt, and baking powder until just combined. Scoop 9 equal balls of dough, place on the baking sheet, flatten to 1 inch thick, and use a 1/4 cup measuring cup to press a well into the center of each.

Bake for 8-9 minutes. The cookies will look underdone; let them cool completely on the baking sheet to set.

For the mousse, cream the cream cheese and brown sugar until smooth. Mix in the pumpkin puree, pumpkin pie spice, and food coloring.

In a separate bowl, whip the cold heavy cream, sugar, and vanilla to stiff peaks. Gently fold the whipped cream into the pumpkin mixture.

Pipe the mousse into the center of each cooled cookie, tap the cookies on the counter to spread the filling, and chill for 30 minutes before serving.