Put Ketchup (1 tablespoon), Mild Mustard (1 tablespoon), Mild Curry Powder (1 tablespoon), Dried Thyme (1/4 teaspoon) and Worcestershire Sauce (1 tablespoon) into a little bowl. Stir until combined.
On an aluminium foil, spread the sauce on each Chicken Thighs and Drumsticks (4).
Divide the Button Mushroom (100 gram), Red Bell Pepper (1) and Yellow Onion (1) over the four chicken pieces. Top it with some Butter (50 gram).
Wrap the foil on the chickens until they are completely enclosed and put them into a baking dish. Preheat the oven to 180 degrees C (350 degrees F) and put in the dish for about one hour. When done, you can serve.