Warm the milk to approximately 110°F (43°C). It should feel pleasantly warm rather than hot.
Add the yeast and granulated sugar to a large mixing bowl or the bowl of a stand mixer. Pour in the warm milk and gently whisk.
Loosely cover and leave for 5–10 minutes. If using active dry yeast, the mixture should begin looking creamy and foamy.
Add the softened butter, egg, flour, salt, garlic powder, and chopped rosemary.
Mix on low speed for about 3 minutes, or stir by hand with a sturdy wooden spoon, until a soft dough forms and begins pulling away from the sides.
If the dough is excessively sticky, add extra flour 1 tablespoon at a time. Keep the dough soft and slightly tacky rather than dry.
Knead with a dough hook for approximately 5 minutes. Alternatively, knead by hand on a lightly floured work surface for about 5 minutes.
Shape the dough into a ball and place it in a lightly greased bowl. Cover and leave in a warm location for 60–90 minutes, or until approximately doubled in size.
Meanwhile, grease a 9×5-inch loaf pan.
Prepare the filling by combining the softened butter, rosemary, parsley, minced garlic, and salt. Mix until evenly blended and keep at room temperature.
Once the dough has risen, gently punch it down to release excess air.
Transfer it to a lightly floured surface and divide into 12 approximately equal pieces.
Flatten each portion into a roughly 4-inch circle. The shapes don't need to be perfect.
Spread each dough circle with 1–2 teaspoons of the rosemary garlic butter.
Sprinkle approximately 1 tablespoon of shredded cheese over each piece.
Fold each circle in half and arrange the folded pieces upright in the prepared loaf pan, with the rounded edges facing upward.
Cover the pan and allow the Rosemary Garlic Pull Apart Bread to rise for approximately 45 minutes, until noticeably puffy.
Position an oven rack in the lower third of the oven and preheat to 350°F (177°C).
Bake for approximately 45–50 minutes, until deeply golden and baked through. If the top becomes too brown before the center is finished, loosely tent it with aluminum foil.
Remove from the oven and place the pan on a wire cooling rack.
If desired, brush the warm loaf with melted butter and sprinkle lightly with flaky sea salt.
Cool in the pan for about 10 minutes before carefully removing and serving warm