Three Potato Soup

Bahan-bahan (6 porsi)

• 3 tablespoons butter
• 1 small white onion, diced
• 4 cloves garlic, minced
• 1/4 cup all-purpose flour
• 2 cups vegetable stock or chicken stock
• 2 cups milk, warmed
• 1/2 pound red potatoes, diced
• 1/2 pound Yukon gold potatoes, diced
• 1/2 pound sweet potatoes, peeled and diced
• 1 cup freshly-shredded sharp cheddar cheese
• 1/2 cup plain Greek yogurt or sour cream
• 2 teaspoons Old Bay seasoning (or Cajun seasoning)
• fine sea salt and freshly-ground black pepper
• optional toppings: thinly-sliced green onions or chives, extra shredded cheese, sour cream