Within the pan used for the meatballs, soften 4 tablespoons butter over medium warmth. Whisk within the flour and prepare dinner roux till golden, 2 to three minutes. Whisk within the rooster inventory; convey to a boil over medium-high warmth, whisking always, till thickened, 2 to three minutes. Flip off warmth. Steadily add the yogurt, about 1 Tablespoon at a time, whisking between additions till easy. Season to style with salt and pepper. Add the meatballs into the gravy; cowl with a lid or foil and prepare dinner over low warmth till cooked by way of, 5-8 minutes.