In a saucepan, heat 3 tablespoons butter and saute onions, mushrooms, ham and pork belly until onions are soft. Strain and reserve the juice. Let cool.
Rub duck inside out with 1 tablespoon butter, salt and pepper. Stuff and truss duck.
Heat oil and deep fry duck until skin is browned.
Remove from oil and in another pan, braise with reserved juice.
Add stock, leek stalk and bay leaves. Braise in low heat until duck is cooked.
Season with salt, pepper and sherry.
Braise pechay with stock until half done. Arrange the vegetables to garnish platter.
Simmer the remaining braising liquid and serve as sauce.
When cooked, keep the bird warm. Serve sliced over pechay.