Preheat oven to 350F and line a baking sheet with parchment paper. Cut the sheet of rolls in half lengthwise. Lay the bottom half of the rolls on the parchment paper.

Peel onion and cut in half. Slice into thin slices. Use kitchen shears to cut the slices of shaved beef into smaller pieces and set aside.

Heat oil in a frying pan over medium heat and add onion to the pan.

Saute onion, tossing frequently for 15 minutes. Add the brown sugar and a pinch of salt to the onions and continue sauteeing for another 3 minutes. Remove the onions from the pan and set aside.

Add the shaved beef to the pan and season with salt and pepper. Saute for 4-5 minutes - until just cooked through. Remove the pan from the heat. 

Assemble the sliders with a layer of cheese on the bottom rolls, then the sauteed beef, then the sauteed onions, another layer of cheese and finally the top of the rolls.

Melt the butter and brush it over the top of the rolls. Sprinkle the sesame seeds on top.

Bake in the oven at 350F for 7 minutes. Remove and cut into individual sliders before serving.