Reduce the heat to as low as possible. Add butter to the pan, allowing it to melt and start to foam before slowly pouring in the marsala – it will sizzle and spit a little at first, so go steady. Then add the lemon zest and juice, capers and parsley, stirring well to make a smooth sauce, scraping the lovely caramelised sticky bits off the base of the pan as you go. Add the chicken back to the pan, and simmer gently to reheat. Taste to check the seasoning, adding a little more salt and pepper if you like. Serve immediately.