Heat the olive oil in a large, deep pan with a lid. Add the steak pieces and fry until they have a nice colour, then stir in the flour and seasoning and cook until the steak has browned all over. Remove from the pan.
Add the butter and melt, then add the mushrooms and onions and cook until the mushrooms let off some water, then add the liquids and thyme and deglaze some of the sticky bits from the bottom of the pan. Bring to a simmer and cover with a lid and leave, stirring occasionally, for about 40 minutes, or until the beef has softened. Preheat the oven to 180°C/360°F.
Lay the bottom halves of the slider rolls in a baking tray and top with 12 layers of cheese. Using a slotted spoon take some of the beef onion mix and spoon it onto each roll then top with more cheese and the top of the rolls. Spoon over the excess gravy and bake for 30 minutes, basting with more gravy if necessary.