In a large skillet over medium-high heat, melt butter. Cook onion and garlic for 2 minutes. Stir in pumpkin, vegetable broth, sage, salt and pepper. Add mixture to slow cooker crock.
Cover slow cooker and cook on HIGH for 2 hours or LOW for 4 hours.
Stir in milk and set on WARM for 30 minutes before serving.
Serve with sour cream, crumbled bacon and pumpkin seeds.