Roast Beef Sliders with Horseradish Cream Recipe - Blue Plate Mayonnaise

Ingredients

• 1 large onion, thinly sliced
• 4 tablespoons unsalted butter, divided
• 1/4 teaspoon coarse salt, plus extra to taste
• 1/4 teaspoon freshly ground black pepper
• 1/2 cup Blue Plate® Mayonnaise
• 1/4 cup sour cream
• 2 tablespoons prepared horseradish
• 1 tablespoon Parmesan cheese, finely grated
• 1 tablespoon basil leaves, finely chopped
• 1 tablespoon shallots, finely minced
• One 12-pack Hawaiian soft rolls or other soft dinner rolls
• 1 pound roast beef, thinly sliced
• 1/2 pound provolone cheese, thinly sliced