Preheat the oven to 350 degrees. Line a baking sheet with aluminum foil and spray with cooking spray.
Slice the rolls in half horizontally to separate the top and bottom, keeping them together as one slab. Do not break into individual rolls.
Place the bottom half on the baking sheet.
Heat 1 tbsp olive oil in the skillet. Season the steak with salt and pepper and cook over medium heat until done, remove from skillet and place on top of the bottom slab of rolls.
Take about 10 pieces of your sliced onion and set aside. In the same skillet heat the remaining 1 tbsp olive oil and cook green pepper and remaining onion together until tender.
Place the green pepper and onion on top of the steak.
Top everything with 8 slices of provolone cheese. Place the other half of rolls on top.
Melt butter and concentrated beef stock together. Stir to combine. Brush mixture over top of rolls. Finely dice reserved onion slices and sprinkle over top of rolls.
Bake in preheated oven for 10 minutes, or until cheese is melted and tops have started to brown. If necessary, cover rolls with aluminum foil to prevent them from browning too much.
Slice into individual sliders and serve warm.
TIPS & NOTES:
When shopping for the meat for your sliders, if your grocery store doesn’t carry thinly sliced steak in the meat section, you can ask the butcher to slice it thin for you. If you prefer to slice it yourself at home, place the meat in the freezer. It makes it easier to slice! Just don’t let the meat freeze all the way through.
If you find that the tops of your rolls are cooking too fast you can cover the rolls with aluminum foil to prevent them from browning too much. You can put the foil on for the entire bake time, or add it when you notice them getting a little bit too brown while baking.