Melt the butter with the garlic, thyme, and sage in a large pot set over medium heat. Allow the butter to brown around the garlic, 3-5 minutes. Once browned, remove the sage leaves and set aside. To the pot, add the pasta and toss with the butter. Add 4 cups of water and bring to a boil over high heat. Add 1 1/2 teaspoons salt. Cook, stirring occasionally, for 8 minutes. Do not drain the water. Stir in the milk, cream cheese, and pumpkin, and cook until the cream cheese has melted and the pasta is al dente, about 4-5 minutes more. Pick out the garlic cloves and set aside. Add the cheddar and Gouda, onion powder, paprika, cayenne, and nutmeg, and stir until melted and creamy. Remove from the heat. If desired, chop or mash the garlic and stir in the pasta. Season with salt and pepper. If the sauce feels thick, add ¼ cup milk or water to thin.Divide the mac and cheese between bowls. Top with black pepper, the reserved sage, and grated nutmeg.