1) Heat an outdoor grill or grill pan to high. If cooking indoors, char the peppers over an open gas flame on the stove top or under a hot oven grill. Char the peppers until blackened all over, then put them in bowl and cover with cling film to cool. If cooking outside, char peppers over the hot area of the grill.
2) In a food processor combine the wine, rosemary, red chilli flakes, garlic and mustard. With the processor running, slowly stream in the extra-virgin olive oil to make a marinade. Season with salt and pepper, to taste. Add the chicken to a resealable plastic bag and pour in 1/3 of the marinade and toss to coat. Add the mushrooms and onions to a small bowl and pour in the remaining marinade.
3) Remove the chicken from the marinade and grill for 12 minutes. Grill the mushrooms and onions until tender, about 8 to 10 minutes and char the tomatoes the last 3 to 4 minutes of cook time.
4) Remove the chicken from the grill to a cutting board and slice on an angle. Serve 1 1/2 thighs per person or 1 breast per person. Pile the chicken on the roll bottoms.
5) Top the chicken with smoked cheese and sliced grilled mushrooms and onions, and squished fire-charred tomato. Peel, seed and chop the peppers and put them on top of the tomato. Sprinkle with a little parsley and cover with the roll tops.
If you're felling ambitious, you can puree the peppers in food processor to make them saucy. Serve the panini with olive oil potato crisps alongside.