Melt butter and pour into 8" square or 9"x7" rectangular dish.
In a large mixing bowl, whisk together flour, baking powder, and salt. Add shortening and cut it in with a fork or pastry cutter. The dough should resemble coarse crumbs.
Add sour cream and stir in with wooden spoon.
Add 7-UP and stir in. The dough will be sticky and shaggy.
Flour flat surface (like your countertop) and place the dough onto it. Form into square or rectangle, roughly the same size as your dish. It is helpful to place the dish right next to the dough for a visual reference.
Cut the dough into biscuits. (see note)
Place biscuits in a dish with butter.
Place in oven and bake for 16 to 18 minutes or until the tops of the biscuits are golden.
Remove from oven and let cool.
Notes
You can cut out the biscuits with a round biscuit cutter but you will be left with some dough. It is easier to cut the dough with a knife into square biscuits. That way you will use the whole amount of dough without scraps.