Preheat oven to 350°F. Line a 9-inch springform pan with foil and grease with cooking spray.

In a bowl, whisk together flour, sugar, cocoa powder, baking soda, and salt.

Add sour cream, oil, egg, and 1 tsp vanilla extract to the dry ingredients, stirring until well combined.

Pour batter into the prepared pan and spread evenly. Bake for 25-30 minutes or until a toothpick comes out clean. Cool completely.

Spread fudge sauce over the cooled cake layer and freeze for 1 hour.

Spread softened vanilla ice cream over the fudge layer and freeze for 2 hours until firm.

For the whipped cream, beat heavy cream, 3 Tbsp sugar, and 1 tsp vanilla extract until stiff peaks form. Spread over the frozen ice cream layer.

Freeze the cake for at least 1 hour, then wrap in foil to prevent freezer burn and freeze until firm, about 1 hour more.

Before serving, let the cake sit at room temperature for a few minutes to soften slightly for easier slicing.