Melt butter in a skillet

Whisk in flour until lightly browned, approximately 1 minute

Gradually whisk in vegetable broth and cook, whisking constantly, until slightly thickened, about 1-2 minutes

Stir in sour cream

Season with salt and pepper, to taste

Stir in meatballs and cook, stirring occasionally, until heated through and thickened, about 20 minutes