Pour boiling water from the kettle into a 2 quart saucepan, place on a high heat and add a pinch of sea salt. Add your rice, bring back to a boil, then turn the heat down slightly. Cook for the length of time given in the instructions on the package.
Cut both ends off the leek, quarter lengthways, slice across thinly, then wash well under running water. Slice the mushrooms. Slice the chicken breasts into little, finger-size pieces.
Put a large frying pan on a high heat and add a good lug of olive oil and a pat of butter. Add the leek to the pan with the white wine, a small glass of water, and a good pinch of salt and pepper. Let it bubble away for 5 minutes, covered loosely with a piece of aluminum foil. Meanwhile, finely chop the parsley, stalks and al. Remove the foil and add the chicken strips, most of the parsley, the cream, and the mushrooms. Stir, bring back to a boil, then turn the heat down to medium and simmer for 10 minutes. Drain your rice. Just before serving, cut your lemon in half and squeeze the juice of one half into the stroganoff. Season to taste.
Spoon some rice onto each plate and top with the stroganoff. Scatter with the rest of the chopped parsley. Serve with the other lemon half, cut into wedges.