For base: melt butters together. stir in peanuts and graham crumbs. Reserve 3/4 cup for topping. Press into 9 x 13 pan.
For filling: mix cream cheese, sugar, peanut butter & vanilla. Add eggs, one at a time. Fold in cool whip. pour over base. Drizzle brown cow on top and swirl through with a knife. Sprinkle 3/4 cup crumbs over top, with extra peanuts. Freeze at least 6 hours.
Before cutting, let sit for about 15 minutes at room temperature. A pizza cutter works great.