Sweet Potato Stuffed Shells

Ingredients (14)

• 2 large yams, boiled and mashed
• 1 onion, diced
• 2 cloves garlic, minced
• 6 fresh sage leaves, minced
• 3 tablespoons unsalted butter
• 1 teaspoon red pepper flakes
• 1/2 cup Greek yogurt
• 1/3 cup heavy cream
• 1/2 cup walnuts, chopped
• 1 28 ounce can tomato sauce
• 6 ounces mozzarella cheese, sliced
• 16 ounces pasta shells, cooked *al dente
• Salt and pepper
• Fresh chives (garnish)