2 cups finely ground cream-filled chocolate sandwich cookies (such as Oreo®)

5 tablespoons unsalted butter, melted

2 tablespoons firmly packed brown sugar

1 pinch salt

1/4 cup unsalted butter, softened

2 tablespoons vegetable oil

1/2 cup white sugar

1/2 cup firmly packed light brown sugar

1 large egg, at room temperature

2 teaspoons vanilla extract

1 cup canned pumpkin puree (not pumpkin pie filling)

1/2 cup full-fat sour cream, at room temperature

1 1/4 cups cake flour

1 1/2 teaspoons ground cinnamon

1/2 teaspoon salt

1/2 teaspoon baking powder

1/4 teaspoon ground nutmeg

1/4 teaspoon baking soda

1/4 teaspoon ground cloves

1/4 teaspoon ground allspice

1/2 cup unsalted butter, softened

4 ounces full-fat cream cheese, chilled

1 3/4 cups confectioners’ sugar, or to taste

1 teaspoon vanilla extract

1/8 teaspoon salt

1/2 cup finely ground cream-filled chocolate sandwich cookies (such as Oreo®)

3 tablespoons black cocoa powder

2 tablespoons heavy cream

16 Oreo cookies, for garnish (optional)