I use a heavy and very large cast iron saute pan for cooking frying pan style. If you only have a small frying pan, it might be easier to cook the caramelised onions and chicken separately. Add rapeseed oil to your pan. I add the full sized pieces of chicken and cook both sides for a few minutes before taking them out of the pan and cutting them into smaller pieces.
When the chicken is cooked through, add the mango chutney, black peppercorns and caramelised onions. Allow the mix to cook slowly for five minutes, turning frequently to stop it burning.
While the mix is cooking, squeeze the lemon and add the juice to the pan.
Prepare the bread for the filling by buttering one side if you spreads (I have a Kenwood panini maker which gets used for lots of different things, but doesn’t need butter on the outside of the bread in the way that some sandwich makers do).
Top the bread with sandwich filling and simply add the second slice of bread.
Toast in the panini maker for a few minutes until ready. (you might use a sandwich maker or simply put it under the grill, but grilling will mean you need to turn it over half way through).
Garnish and serve.