Philly Cheesesteak Sliders

Ingredients

1 pound shaved steak I used Trader Joe's
1 cup chopped yellow onion
3 cups chopped white button mushrooms
6 ounces thinly sliced cheese American or Provolone
olive oil
salt and pepper
12 slider rolls I used Trader Joe's Aloha Rolls
mayonnaise optional, but good
1 1/2 Tablespoons melted salted butter

Instructions

Prepare the filling:

Preheat oven to 350 degrees F. Line a baking pan large enough to fit your rolls with foil. Spray with cooking spray. (Mine fit into a 9" square pan.) Set aside.
In a large frying pan, fry the chopped onions in about a tablespoon of olive oil until they have some deep golden brown edges. Salt and pepper to taste. Remove the onions from the pan and set aside.
Add another splash of olive oil to the same frying pan you used to fry the onions, and cook the chopped mushrooms until they start to get golden. They will give off a lot of water at first. You'll have to cook them until that water evaporates before they start to brown a little. Salt and pepper to taste. Remove from pan and set aside.
In the same pan, heat up just a bit of olive oil and flash fry the shaved steak. I had to do about four batches so that the pan wasn't over crowded. If you add too much meat, you won't brown it, you'll steam it. Each batch should only take a minute to quickly brown. Don't over cook. Some of my pieces had some bits of pink left. Remember, they're still going to bake in the oven. I salted and peppered each batch to taste.
Chop or pull apart the steak into small pieces. I used gloved hands to do this. It was much faster than chopping with a knife.
Cut slider rolls in half horizontally. If desired, spread both top and bottoms with mayonnaise. Place the bottom half of the rolls into the prepared pan.

To assemble the sliders:

Layer the bottom of the rolls with about 6 slices of cheese or enough to fully cover the rolls. Top the cheese layer with steak, then onions, then mushrooms. Finish with another 6 slices of cheese.
Brush the top of the rolls with melted butter. Cover with foil and bake for 20 minutes. Remove foil and bake for another 5 minutes or until tops of rolls are toasty.
Use foil to lift the sliders out of the pan. Cut and serve.

Recipe Notes

*I recommend that you use a good shaved steak for this recipe. I use a shaved steak from Trader Joe's. Or you can ask your butcher to shave ribeye steak for you. I wouldn't use those individual quick cooking thin "steaks" you often find in the freezer section.

*I only use one pan to cook the filling ingredients. I start with the onions. When they're done, I take them out of the pan and add the mushrooms. When they're finished, they'll get set aside and I'll cook the steak. At that point, the steak will pick up all the residual flavor from the onions and mushrooms that were previously cooked in the pan. Yum!

*I think these are best served fresh out of the oven. If you have leftovers, wrap them in foil and store them in the refrigerator. Reheat them in a 350 degree oven, fully wrapped in foil, for about 30 minutes or until nice and hot. They're going to take longer than the first time you baked them because now they're cold. You can uncover them again to re-toast the tops. Alternatively, you can remove the foil and quickly reheat them in the microwave.

*If you don't want to use mayonnaise, it's fine. The cheese will form an effective barrier for any rebel juices. Or, you could opt to toast the cut sides of the bread briefly under the broiler, but it's not necessary.