1 1/2 pounds sweet potatoes; peeled and 1/2-inch diced
2 Tablespoons salted butter
2 Tablespoons vegetable oil
1 Cup diced onion; 1/2-inch cubes
1 Cup diced celery; 1/2-inch cubes
2 cloves garlic; minced
1 Cup diced red bell pepper; 1/2-inch cubes
1 Cup diced green bell pepper; 1/2-inch cubes
1/4 teaspoon red pepper flakes; crushed
Salt and freshly ground black pepper
Place the diced potatoes in a medium pot, cover with 2 inches of cold water, and generously season with salt. Over high heat bring to a boil, reduce the heat to medium, and simmer for 5 minutes. Drain and set aside.
In a large non-stick skillet over medium heat, melt the butter and heat the oil. Add the onion and celery and cook for 10 minutes, until the onions are soft.
Add the garlic and continue to cook for 3 minutes, stirring constantly. Add the red and green peppers, and red pepper flakes, and continue to cook for 5 minutes.
Add the potatoes and cook until they are just heated through, about 1 minute.
Season with salt and pepper to taste. Serve hot.