Preheat oven to 350°F (175°C). Grease two 8x8 inch pans and line the bottoms with parchment paper, leaving an overhang on the sides.

In a medium bowl, combine melted butter, granulated sugar, and brown sugar. Mix with a hand mixer on medium speed.

Add eggs one at a time, mixing well after each addition. Stir in vegetable oil and vanilla extract.

In a separate bowl, whisk together flour, cocoa powder, and salt. Gradually add the dry ingredients to the wet ingredients, mixing on low speed until just combined.

Divide the brownie batter evenly between the prepared pans and spread gently with a spatula. Bake for 30-40 minutes, or until a toothpick inserted into the center comes out with moist crumbs.

Let the brownies cool in the pans for 10 minutes. Use the parchment paper to lift the brownies out onto a cooling rack. Peel the parchment off only one of the brownie halves. Let cool completely to room temperature.

Soften the ice cream slightly for 5-10 minutes. Place the brownie half with the parchment paper still attached back into one of the pans. Spread the softened ice cream evenly over the brownie.

Invert the second brownie half on top of the ice cream. Cover the pan tightly with plastic wrap or aluminum foil.

Freeze for at least 6 hours, or preferably overnight, until firm.

When ready to serve, remove the pan from the freezer and let it sit at room temperature for 5-10 minutes. Use the parchment paper to lift the entire block out. Cut into 8 equal squares with a sharp knife.