when a recipe calls for instant coffee dissolved in sour cream, is this granules?

Agree with Lori T the recipe means instant coffee granules.
But in a pinch, I have used ground coffee - if you're one of those people who can stand black pepper in a white sauce.
If the coffee is ground finely enough, it gives flavor to the sour cream, and only a slight (not unpleasant) grittiness.

The only "mud" recipe I know of that uses both sour cream and coffee is a Mississippi Mud Cake. In that case, you will use dry instant coffee granules, not liquid coffee. Liquid coffee would likely upset the liquid/dry ingredient ratio.