Combine the warm milk, yeast and sugar in the bowl of a stand mixer, and let sit 5 to 10 minutes until foamy on top.

Add the egg and 4 tablespoons of the melted butter, whisking to combine.

Add the flour and salt, mix with the dough hook on low 2 minutes until shaggy, then increase speed and knead 6 to 8 minutes until the dough is smooth and springs back when poked.

Transfer the dough to a greased bowl, cover with a towel, and let rise in a warm spot 1 hour until doubled in size.

Punch down the dough, divide into 15 equal pieces, and roll each into a tight ball.

Arrange the rolls in a greased 9x13 inch baking dish, leaving small gaps between them for the second rise.

Cover loosely and let rise 30 to 40 minutes until the rolls are touching and puffy.

Preheat the oven to 350F.

Bake 22 to 25 minutes until the tops are deep golden brown and the rolls sound hollow when tapped.

Brush the warm rolls with the remaining 2 tablespoons melted butter and sprinkle with flaky salt if using.