1 stick (8 tablespoons) salted butter, softened
6 everything bagels, split
2 medium yellow onions, halved and sliced
1/4 cup mayonnaise
2 tablespoons yellow mustard
Hot sauce, as needed
Kosher salt and freshly ground black pepper
1 pound bulk hot breakfast sausage
1 pound bulk maple breakfast sausage
12 slices Cheddar
6 large eggs