Step 1: Activating the Yeast (The Foundation)
Start by combining your warm milk (strictly between 105°F and 115°F), active dry yeast, and a pinch of your granulated sugar in the bowl of a stand mixer. Let it sit for 5 to 10 minutes. Pro Tip: If the mixture doesn’t turn frothy and bubble up, your yeast is likely expired, or the milk was too hot. Do not proceed until you have a bubbly base!Step 2: Mixing the Brioche Dough (Building Structure)
Once the yeast is activated, whisk in the remaining sugar, melted butter, and the room-temperature egg. Gradually add 2 cups of the all-purpose flour and the salt. Attach the dough hook and mix on low speed. Slowly add the remaining flour, 1/4 cup at a time, until the dough pulls away from the sides of the bowl. Knead for 5 minutes until smooth and elastic.Step 3: The First Rise (Patience is Key)
Form the dough into a ball and place it in a lightly oiled bowl, turning once to coat. Cover with a warm, damp towel or plastic wrap. Place it in a draft-free spot for about 1 hour, or until the dough has doubled in size.step 4: Rolling and Filling (The Flavor Center)
Punch down the risen dough and turn it out onto a lightly floured surface. Roll it into a large rectangle, roughly 10x16 inches. Spread your softened butter evenly across the dough, leaving a small border. Sprinkle your mixture of brown sugar, cinnamon, and nutmeg generously over the butter.Step 5: Shaping the Ring and Second Rise (The Classic Look)
Starting from the long side, roll the dough up tightly like a cinnamon roll. Bring the two ends of the log together to form an oval ring, pinching the seams securely to seal. Transfer the ring to a parchment-lined baking sheet. Cover lightly and let it rise for another 40 minutes until puffy.Step 6: Baking to Golden Perfection
Preheat your oven to 350°F (175°C). Bake the King Cake for 20 to 25 minutes. You are looking for a deep, golden-brown crust. Actionable Tip: If the top is browning too quickly, tent it with aluminum foil for the last 10 minutes of baking. Let the cake cool completely on a wire rack.Step 7: Icing and Decorating (The Mardi Gras Magic)
Once completely cool, whisk together the powdered sugar, vanilla, and milk until you reach a thick, pourable glaze. Drizzle the icing generously over the cake. Immediately sprinkle wide bands of purple, green, and gold sugar over the wet icing. Finally, carefully tuck the plastic baby underneath the cake (never bake the baby!).