Preheat oven to 450 degrees.
In a large bowl, sift together the flour, Bisquick, baking powder, sugar, salt.
Cut butter into pats and add to dry ingredients.
Using a pastry cutter or fork, cut in the butter until small "pebbles" form,
Combine milk and buttermilk.
Gradually pour in the liquid while stirring with a spoon until just combined.
If the dough is too wet, add a little more flour, just until the dough is able to be handled.
Turn out onto floured surface, dust top with flour and form into just over 1/2" thickness.
Cut circular shape with a biscuit cutter, jar lid, or drinking glass. Dip cutter in flour as necessary to avoid sticking.
Place biscuits on a baking sheet.
Bake for 10-15 minutes until tops are lightly browned.
Brush tops with melted butter.