Yes, I've made them with sour cream,  however, the recipe doesn't have garlic& I didn't use it.  Do
you have any chile in adobo?  I have a recipe in my file from Fine Cooking Magazine that uses 1/4 cup sour cream, 1/2 chile in adobo, minced to a paste...more to taste, 2 T. butter, salt and pepper.  Served with extra sour cream and lime quarters.  That's for 4 small sweet potateos, 3 lbs total...I wouldn't call those small, lol. Hope that helps.