Horseradish Mashed Potatoes With Caramelized Onions Recipe

Melt butter in large skillet over medium heat. Add onions; sauté until deep golden, about 30 minutes. Add vinegar and thyme. Reduce heat to low; sauté 4 minutes. Season with salt and pepper.

Meanwhile, cook potatoes in large pot of boiling salted water until very tender; about 20 minutes. Drain. Return to same pot; mash until smooth. Add 3/4 of the milk, horseradish and butter; stir to blend. Thin with remaining milk if necessary. Season with salt and pepper. Transfer potatoes to serving dish.

Spoon onion mixture on top of potatoes. (Can be prepared 8 hours ahead. Cover with foil and refrigerate. Rewarm in 350 degree oven about 30 minutes.) Serve hot.