Preheat oven to 450°F.
Mix the Bisquick, buttermilk and sugar together in a bowl.
Add the melted butter into the batter.
Stir until a soft dough forms.
Turn out onto a well floured work surface.
Knead 20 times (this is a very forgiving dough), and don't be afraid to get additional flour into the dough.
Roll 1/2 thick, or thicker if you prefer towering biscuits.
Punch out biscuits with a round cookie cutter.
Place close together on an ungreased baking sheet.
Brush tops with melted butter.
Bake for 8 to 10 minutes; I usually find 8 minutes is enough.
When you remove the biscuits from the oven, brush the tops with melted butter again.