Horseradish Mashed Potatoes With Caramelized Onions

• 1/4 cup butter
• 2 1/4 lbs white onions, thinly sliced
• 3 tablespoons balsamic vinegar
• 2 teaspoons fresh thyme, chopped
• 3 1/2 lbs russet potatoes, peeled, cut into 1-inch pieces
• 7 tablespoons whole milk
• 1/4 cup prepared horseradish
• 6 tablespoons butter

1. Melt 1/4 cup butter in large skillet over medium heat. Add onions; saute until deep golden, about 30 minutes. Add vinegar and thyme. Reduce heat to low; saute 4 minutes. Season with salt and paper.
2. 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 6 tablespoons milk, horseradish and 6 tablespoons butter; stir to blend. Thin with 2 tablespoons milk if necessary. Add 1 to 2 tablespoons more butter if necessary. Season with salt and pepper.
3. Transfer potatoes to serving dish. Spoon onion mixture atop potatoes. (Can be prepared 8 hours ahead. Cover with foil and refrigerate. Rewarm in 350u0b0F oven about 30 minutes). Serve hot.

butter, white onions, balsamic vinegar, fresh thyme, russet potatoes, milk, horseradish, butter

Taken from www.food.com/recipe/horseradish-mashed-potatoes-with-caramelized-onions-179708 (may not work)