Recipe? I wing it. My father never shared his method with me except I learned you need decent marsala and a heavy hand with the bottle.
Cut chicken breasts into cubes about 2-3 cm diameter. Dredge in flour, salt, and pepper. Brown. Pull chicken out. Turn down heat and saute chopped onions with salt and pepper to taste. Chopped shallots are nice, too but I think using only shallots is too much so a mixture with onions if you go that way. When onions are soft add sliced mushrooms and chopped garlic and cook until soft. glug in, oh, a third to half bottle of marsala per 2 breast halves and deglaze the pan. The flour from the chicken should be enough to thicken the sauce. Adjust salt and pepper. Serve over pasta.
Keep it simple.