Cacciatore chicken with potato mash (variation of pollo alla cacciatora- hunter's chicken)

Recipe belongs to Rachael Ray, I just made some convenient for me changes. I find it very tasty, cosy and filling, though still not heavy.

potato
salt
olive oil
30gr butter
5 garlic cloves
scallions
about 40ml balsamic vinegar
red pepper flakes+ paprika flakes (to taste)
rosemary, basil
mushrooms  200g (I had large champignons)
about 500 gr chicken meat
1 green bell pepper
1 small onion
2 big tomatoes and tomato paste
pepper, salt, paprika
parsley
milk
about 80g Parmigiano

Put potatoes to boil with some salt. Simmer for 2-3 minutes garlic(3 cloves) and scallions in butter and oil. Set aside, take the onion out.
In a bowl mix herbs, vinegar, olive oil (about 70ml) and pepper flakes. Put for a minute mushrooms and chicken meat in this marinade, then grill chicken from both sides, after- mushrooms (season with pepper).
In a pan where olive oil and butter are left cook 2 cloves garlic, onion and bell pepper, add tomatoes, paste, some water and pinch of sugar and season.
Slice mushrooms and chicken if the pieces are too big.
Mash potatoes with milk and cheese, scallions and garlic from a pan and season with salt and pepper. Put on a plate potato mash, chicken+mushrooms with sauce on top. Serve!