Place the potatoes and garlic in a pot and cover with 2" of cold water. Gently boil the potatoes until tender. When cooked, drain the potatoes well, ensuring the garlic stays in the pot, and then thoroughly mash. Whip in the milk and butter until well combined. Mix in the cheese and green onions, season with salt and pepper, and serve.
Recipe Options: Instead of Gouda, try another type of cheese, such as old cheddar or Gruyere. Instead of green onion, use two tablespoons of snipped, fresh chives in the potatoes. For a tangy taste, instead of milk, use buttermilk in the potatoes.