Preheat the oven to 180C. Using a silicon brush, grease the holes of a muffin pan with melted butter or oil.
Put 3 filo sheets on top of each other and cut out 10 x10 cm squares. Cover them with a towel.
Lay a filo square on a chopping board, brush it with some melted butter/oil, then layer another square on top, slightly turned. Brush this also with butter/oil, then layer another square on top, again angled. Put this shape into one of the tin holes, slightly pushing it down with your fingers.
Repeat with the rest of the filo squares until you get 12 baskets.
Put the muffin tin into the oven for 5 minutes.
Meanwhile, finely chop the mushrooms and red pepper, slice the frankfurters.
Take the muffin tin out of the oven and divide evenly the chopped mushroom, red pepper, beans/peas and frankfurter pieces between the baskets. Scatter the grated cheese on top.
Cook 10 minutes, until golden and the cheese has melted.