Grilled Steak Sandwich with Onion & Horseradish Cream

Ingredients

• 4 La Brea Bakery Take & Bake Torta Rolls
• 2 tablespoons olive oil
• 2 medium yellow onions, sliced
• 1 cup sliced mushrooms
• 1 pound flank steak
• Salt and freshly ground black pepper, to taste
• 4 slices aged cheddar cheese
• 4 tablespoons horseradish cream (recipe below)
• ½ cup sour cream
• 2 tablespoons freshly grated horseradish
• ½ tablespoon Dijon mustard
• ½ teaspoon white wine vinegar
• Salt and pepper, to taste