This dish is normally made with red or fingerling potatoes, but I had purple potatoes delivered in my CSA box. Aren't they pretty? But mashed just seemed wrong. Really, tell me — how often are potatoes so gorgeous? Full disclosure? I do love purple; it's my favorite color!
Preheat the oven to 350 degrees.
Mix together the potatoes, onions, and garlic in a large roasting pan or baking sheet. Coat with olive oil and season with salt and pepper, to taste.
Bake uncovered for 30 minutes. Test potatoes with a fork for doneness; continue to cook in 5-minute increments until the potatoes can be easily punctured with a fork. Season with more salt and pepper, to taste, and serve.