In a large bowl or the bowl of a stand mixer with a dough hook attachment, dissolve the yeast and sugar in the warm water and let stand for five minutes, or until foamy. 

Add butter, salt, and 3 cups of flour. Mix until combined. 

Add additional flour, 1/4 cup at a time, until the dough pulls away from the sides of the bowl and is only slightly sticky to the touch (careful not to add too much flour!).

Knead the dough 3-5 minutes, until smooth. Cover with a towel or plastic wrap and let rise for 20 minutes.

Preheat the oven to 400 degrees F and line a 9 x 13 pan with parchment paper or spray with nonstick cooking spray. Gently punch the dough down and divide into 20 equal sized pieces. Roll each piece into a ball and space evenly in the prepared pan. 

Brush with melted butter, sprinkle with sea salt, and let rise for an additional 15-20 minutes. Bake 13-15 minutes, or until golden brown. Remove from the oven and brush with more melted butter. 

Let cool for 10 minutes before serving.