Created by SueFreedman on June 19, 2012
Step 1: Creamy Horseradish Dressing: In bowl, whisk together mayonnaise, milk, horseradish, garlic, salt and pepper (I would start with 6 tablespoons horserashish then adjust to you liking, can make ahead and chill).
Step 2: In large skillet, heat oil over medium-high heat; saute mushrooms, 1 clove minced garlic and thyme until no liquid remains and mushrooms are golden, about 5 minutes. Season as you desire with salt and pepper.
Step 3: Divide spinach among 4 plates. Divide mushrooms, steak slices and onion over top; drizzle with dressing.