Heat oven to 350°F. Grease 9-inch square baking pan. Stir together butter, sugar and vanilla in bowl. Add eggs; beat well with spoon. Stir together flour, cocoa, baking powder and salt; gradually add to egg mixture, beating until well blended. Stir in nuts, if desired. Spread batter evenly in prepared pan. Bake 20 to 25 minutes or until brownies begin to pull away from sides of pan. Cool completely in pan on wire rack! Cut into even squares for serving. You can also frost these with your favorite fudge buttercream if you desire to!
Put about 10 cups ice in the container, filling it about three-quarters of the way, then pour in the sea salt. Nestle the sealed bag of buttermilk mixture in the ice. Start shaking! Tightly cover the container with the lid. Shake vigorously for about 15 minutes, or until the buttermilk mixture is thick. How long it takes depends on your shakin'! OR...put it in your home ice cream maker and prepare according to the manufacturer’s instructions.