OK, I am totally stealing this idea from Elise at Simply Recipes, but I adapted it to be just potatoes, instead of with spinach and sausage. Spinach and sausage are great, but I didn't have any... I just had a lot of potatoes :) Here is the 4 person side-dish serving size version, but I tripled this to bring to a potluck today. It worked well for a make-ahead potato dish, which I can't say about too many other potato dishes...
3 medium potatoes, peeled and cut into 1" chunks
1 tsp. olive oil
1 medium onion, thinly sliced
1 clove garlic, pressed
1/4 c. milk
1 1/2 T. butter (+ additional butter for dish)
2 T. chicken broth
1 T. cider vinegar
1/2 tsp. salt
1/8 tsp. pepper (just "eyeball it" as Rachael Ray says and grind some over the top)
1 c. shredded mozzarella, parmesan, swiss, cheddar, or ??? cheese
1. Butter a 4x6 or 8x8 baking dish. Preheat oven to 400. Place the potatoes in a large saucepan or soup pot. Cover with water 1" above the surface of the potatoes and bring to a boil. Reduce heat and simmer for 15 minutes.
2. Meanwhile, heat the oil in a large skillet over medium-high heat. Add onions and cook until golden, stirring often, about 5-7 minutes. Add garlic and saute 1 minute longer or until fragrant. Remove from heat.
3. Drain potatoes. Wipe pot dry, return potatoes to pot and mash with milk, butter, broth, vinegar, nutmeg, salt and pepper. Stir in half the cheese. Spread potatoes in prepared baking dish. Top with caramelized onion-garlic mixture and remaining cheese. Bake at 400 for 20 minutes to melt cheese and heat through.