In a large bowl, whisk together the melted butter and granulated sugar for a full 2 minutes. This step matters! It dissolves the sugar and creates that fluffy texture.

Add the eggs, vanilla extract, and cake batter extract. Whisk until smooth and combined.

Pour in the sour cream and whole milk and whisk until everything is silky and uniform.

Add the flour, baking powder, and salt right into the bowl, then gently FOLD them in with a spatula until just combined. Do not overmix or your muffins will turn out tough.

Fold in the 3/4 cup of sprinkles, just enough to distribute them evenly throughout the batter.

Make the streusel by stirring together the melted butter, flour, sugar, and sprinkles in a separate bowl until you have big crumbly clumps.

Scoop the batter evenly into your 12 muffin cups, filling each almost all the way to the top. Generously pile that streusel on every single muffin (yes, use ALL of it).

Bake at 400°F for 10 minutes, then WITHOUT opening the oven, drop the temperature to 350°F and bake for another 10 minutes. This is the trick to that perfect bakery dome!

Let the muffins cool in the pan for 5 minutes, then transfer to a wire rack. Try to wait a couple minutes before devouring (good luck).