01 - In a small bowl, combine warm milk and water. Sprinkle yeast and 1 tablespoon granulated sugar over the mixture. Allow to stand until foamy, approximately 5-10 minutes.
02 - In a large mixing bowl, cream together butter and the remaining granulated sugar until light and fluffy. Incorporate eggs, vanilla extract, lemon zest (if using), nutmeg, and salt; mix thoroughly.
03 - Add the activated yeast mixture and half of the all-purpose flour to the bowl, stirring until fully incorporated. Gradually add the remaining flour, mixing until a soft dough forms.
04 - Transfer the dough to a lightly floured surface and knead for 8-10 minutes, or until smooth and elastic. Place the dough in a lightly greased bowl, cover, and let it rise in a warm environment until doubled in size, which typically takes about 1 hour.
05 - While the dough rises, prepare the cinnamon filling. In a separate bowl, combine brown sugar and ground cinnamon. Set aside the softened butter.
06 - Once risen, gently punch down the dough to release air. On a lightly floured surface, roll the dough into a 10x20-inch rectangle.
07 - Evenly spread the softened butter over the surface of the rolled dough, then sprinkle the cinnamon sugar mixture across it.
08 - Starting from one of the long edges, tightly roll the dough into a cylindrical log. Pinch the seam firmly to seal.
09 - Carefully form the log into a ring shape, pinching the ends together to secure them. Transfer the ring to a parchment-lined baking sheet. Cover and let it undergo a second rise until noticeably puffy, approximately 30-40 minutes.
10 - Preheat oven to 350°F. Bake the King Cake for 25-30 minutes, or until it achieves a golden-brown color. Allow the cake to cool completely before proceeding with decoration.
11 - To prepare the icing, whisk together powdered sugar, milk, and vanilla extract in a bowl until the mixture is smooth and has a pourable consistency.
12 - For the colored sugar topping, divide the granulated sugar into separate small bowls. Add a few drops of purple, green, and gold food coloring to each bowl, mixing until the sugar is vibrantly colored.
13 - Once the cake is completely cooled, drizzle the prepared icing over it. Immediately sprinkle the colored sugars in alternating sections (purple, green, gold) onto the wet icing.
14 - If desired, hide a small plastic baby or a dried bean inside the cake after it has cooled and been decorated.