I was making about 72 sandwiches, which was time consuming, buy very easy. Based on all the raves I'm still getting on these sandwiches, it's safe to say they were a huge hit and I won't hesitate to make them again if the occasion calls for it. Even I enjoyed them, with the modifications I made! I highly suggest if you like mayo and mustard though to make the original version because, well, let's face it... I'm weird for not liking those things that most people love!
Also, they're so easy to modify overall flavor profiles. I made half ham & cheese, and the other half turkey & cheese.
Ham & Cheese (Turkey & Cheese, or any Meat & Cheese) Sliders
24 White Dinner Rolls, such as Hawaiian Rolls
24 Slices Honey Ham, Honey Turkey, Roasted Chicken, etc.
24 Small slices Swiss Cheese, or Cheese of your Choice (I used 1/2 a slice per sandwich, based on the slice size)
8 oz. soft cream cheese spread of choice (plain, chive & onion or garden veggie)
1 stick butter, melted
1 tablespoon minced onion
1/2 teaspoon Worcestershire sauce
2 teaspoons yellow mustard
1/3 cup grated Parmesan cheese
Directions:Preheat oven to 350 degrees.
Slice rolls in half, and spread on a thin layer of cream cheese. Place a slice of meat and slice of cheese inside each roll. Close rolls and place into a large baking sheet very close together.
In a medium bowl, whisk together the melted butter, onion, Worcestershire sauce, mustard and Parmesan cheese. Pour evenly over all of the sandwiches. Let sit for 10 minutes, or in fridge overnight, covered), to allow butter to set slightly. Cover with foil and bake for 12-15 minutes or until cheese is melted. Uncover and cook for 2 more minutes. Serve warm.
Source: though these guys are all over the place, and have been feeding families since at least the 80s, the earliest written recipe I can find is at The Recipe Club