How to Make It
Stir together yeast, warm water, and 1 teaspoon of the sugar in the bowl of a heavy-duty stand mixer fitted with paddle attachment. Let stand until foamy, about 5 minutes. Add softened butter, kosher salt, eggs, milk, 3 cups of the bread flour, and remaining 1/4 cup sugar to bowl. Beat on low speed just until dough comes together, about 1 minute. Switch to a dough hook, and with mixer running on low speed, slowly add remaining 1 1/2 cups flour. Continue to beat until dough is smooth but still sticky, about 5 minutes. Turn dough out onto a lightly floured surface, and knead until elastic and almost no stickiness remains. Transfer to a large lightly greased bowl, turning once to grease top of dough. Cover and let rise in a warm place (80ºF), free from drafts, until doubled in bulk or 1 hour.
Turn dough out onto a lightly floured surface, and roll to about 1/4-inch thickness. Brush surface with 2 tablespoons of the melted butter. Cut circles of dough using a 2 1/2-inch round cutter; fold circles in half, and place in 2 lightly greased 9-inch square baking dishes, making 3 rows per dish (8 rolls in each row, overlapping slightly). Reroll scraps once, and brush with 1 tablespoon of the melted butter; cut circles, and place in pan as directed. Cover pans with plastic wrap, and let rise in warm place (80ºF), free from drafts, until almost doubled in size, about 45 minutes.
Preheat oven to 350ºF. Bake rolls until golden brown, 18 to 20 minutes. Immediately brush with remaining 2 tablespoons melted butter, and sprinkle with flaky sea salt. Serve warm.