Heat your oven to 350°F and line a 9x13 baking pan with parchment paper. Cream together your butter and sugar until fluffy—this takes about 2-3 minutes with an electric mixer. Don't skip this step because it helps your Easter peeps treats get that light, airy texture. Add eggs one at a time, beating well after each addition.

Sift together the flour, cocoa powder, baking soda, and salt in a separate bowl. I personally whisk this combo manually because it keeps lumps from forming. Alternate adding the dry ingredients and milk to your butter mixture, starting and ending with dry stuff. This prevents overmixing and keeps everything nice and tender.

Stir in the vanilla powder gently—don't beat it in or you'll deflate all that fluffy goodness you just created. Fold in your marshmallow fluff using a spatula with about 20 slow folds. You'll see streaks of white through the chocolate batter, and that's exactly what you want happening here.

Pour half your batter into the prepared pan and spread it evenly across the bottom. Sprinkle half the chocolate chips over this layer. Pour the remaining batter on top and smooth it out gently.

Top everything with remaining chocolate chips, then press peeps marshmallow candies into the batter however you like. I usually space them in a cute pattern, but honestly, random looks just as good. Drizzle 1/2 cup water over the entire surface—yes, really, it sounds weird but this creates an amazing sauce underneath.

Slide the pan into your preheated oven and bake for 28-32 minutes until the edges pull away slightly from the pan. The center should look almost set but still feel a tiny bit jiggly when you shake the pan gently. Careful not to overbake or the whole thing gets dense and fudgy instead of cake-like.

Let this cool in the pan for about 10 minutes, then transfer to a wire rack if you can. I always leave mine in the pan because it's easier, and honestly it still tastes incredible. The peeps on top get soft and gooey while the cake underneath stays moist and chocolatey.