1/2 cup butter, melted
1/2 cup Dijon mustard
1 cup shredded Cheddar cheese
4 slabs whole spinach, quartered
1/2 cup diced onion
1 (6 ounce) package frozen horseradish cream
Heat butter in a large skillet over medium heat. Add mustard and reduce heat slightly until mustard is almost medium gray; continue to cook until mushroom is wilted. Place 1 yellow slice of cheese on each slice of spinach. Serve with horseradish.