Bloom the yeast: In a large mixing bowl, whisk warm milk with sugar, then sprinkle over the yeast. Let sit until foamy, 5–10 minutes.

Make the dough: Add the egg, melted butter, salt, and 2 3/4 cups flour. Mix until a shaggy dough forms. Knead for 6–8 minutes, adding remaining flour as needed, until smooth and elastic.

First rise: Shape into a ball, place in a lightly oiled bowl, cover, and let rise until doubled, 45–60 minutes.

Make garlic butter: Stir together melted butter, minced garlic, and chopped parsley. Set aside.

Shape the balls: Punch down the dough and divide into 32 equal pieces. Flatten each, place a mozzarella cube in the center, pinch the edges to seal, and roll into a smooth ball. Place seam-side down.

Form the wreath: Line a large baking sheet with parchment. Arrange the balls in a 10–11-inch ring with a smaller inner ring, leaving space between pieces for rising.

Second rise and preheat: Cover loosely and let rise until puffy, 15–20 minutes. Preheat the oven to 375°F (190°C). Once risen, whisk the egg with 1 tablespoon of water and gently brush the dough balls with egg wash just before baking.

Bake: Bake on the center rack at 375°F (190°C) for 18–22 minutes, until deep golden and the centers reach approximately 200°F (93°C). If browning too quickly, tent loosely with foil.

Finish: Brush the hot wreath with garlic-parsley butter and sprinkle with grated Parmesan. Add flaky salt and red pepper flakes if desired.

Garnish and serve: Transfer to a platter, decorate with fresh rosemary sprigs, and serve warm with marinara sauce for dipping.