Variation—For spinach boereg, melt 2 tbsp. butter in a large skillet over medium high heat and saute 1 large chopped peeled onion until golden, 5-8 minutes. Squeeze out excess water from one 10-oz. packaged thawed frozen spinich, add to skillet, season to taste and freshly ground black pepper, and cook until moisture evaporates, 5-8 minutes. Set asid to cool; stir in 1/2 cup chopped fresh dill. Add spinich mixture to fillling in 1, omitting egg and milk, and proceed with recipe.