1. Preparing the Cake Batter

1. Preheat oven to 350°F (175°C) and grease and flour two 9-inch cake pans.
2. In a bowl, whisk together flour, baking powder, and salt.
3. In a separate bowl, beat together butter and sugar until light and fluffy.
4. Add eggs one at a time, mixing well after each addition, then add vanilla extract.
5. Alternately add the dry ingredients and whole milk, beginning and ending with the dry ingredients.
6. Stir in green gel food coloring until you reach your desired shade of green.
7. Divide batter evenly between the prepared cake pans and bake for 30-35 minutes, or until a toothpick comes out clean. Let cool completely.

2. Making the Buttercream Frosting

1. Beat butter in a large bowl until creamy.
2. Gradually add powdered sugar, heavy cream, vanilla extract, and salt, beating until smooth and fluffy.
3. Add more powdered sugar if the frosting is too thin, or more cream if it’s too thick.

3. Assembling the Cake

1. Once the cake layers are cool, remove them from the pans.
2. Place one layer of cake on your serving plate and spread a generous amount of buttercream frosting on top.
3. Stack the second cake layer on top and apply a thin “crumb coat” of frosting to seal in any loose crumbs.
4. Chill the cake in the fridge for 30 minutes to set the crumb coat, then apply the final layer of frosting.

4. Decorating the Cake

1. Use edible silver dust or luster spray to decorate the outside of the cake with silver accents.
2. Decorate with fondant snakes or the Slytherin House crest for a more authentic touch.
3. Add silver sprinkles or edible glitter for extra flair.