01 - In a large bowl or stand mixer, combine bread flour, granulated sugar, active dry yeast, and salt until well blended.
02 - Pour in warm milk, add the room temperature egg, and incorporate softened butter. Mix until a soft dough forms, then knead for 8 to 10 minutes until the texture becomes smooth and elastic.
03 - Divide the dough into three portions: 60% for the red center flesh, 25% for the white rind layer, and 15% for the green exterior skin.
04 - Work red or pink gel food coloring and watermelon extract into the largest portion until evenly distributed. Gently fold mini chocolate chips throughout to simulate watermelon seeds.
05 - Keep the medium portion plain without coloring to create the white rind section.
06 - Thoroughly mix matcha powder or green food coloring into the smallest portion until a vibrant green color is achieved.
07 - Shape each colored portion into a ball and place in separate greased bowls. Cover with plastic wrap or a kitchen towel and let rise for 1 hour until doubled in volume.
08 - Punch down each risen dough. Flatten the red portion into a log the length of your loaf pan. Wrap the white dough completely around the red log, then wrap the green dough around both layers. Pinch seams firmly to seal.
09 - Position the loaf seam-side down in a greased 9x5-inch loaf pan. Cover and let rise for 30 to 45 minutes until puffy and expanded.
10 - Preheat your oven to 350°F.
11 - Bake for 30 to 35 minutes, covering with aluminum foil if the crust browns too quickly during baking.
12 - Allow the bread to rest in the pan for 10 minutes, then carefully remove and transfer to a wire rack. Cool completely before slicing to reveal the watermelon pattern inside.