Thinly slice the onions. Chop the mushrooms.
Mix paprika, ketchup, and brown sugar with vinegar to make the marinade.
Crush garlic, pepper, cloves, and mix with the chicken pieces along with the marinade. Let it sit for 5 minutes.
Heat butter in a pan, and fry the crushed garlic.
Add the chopped mushrooms, and saute on a medium flame.
Once the mushrooms are cooked, add quarter cup of milk. Bring to boil on a low flame.
Let it cool down. Blitz to a thick paste in a blender. You can add 1/4 cup water if required.
Empty the marinated chicken along with all juices to a pot. Add half cup water, mix well, and cook with the lid closed on low flame.
Heat a thick, non-stick pan. Coat the entire surface with a tablespoon of olive oil. Reduce to a low flame, and start frying the onions.
Continue frying the onions while stirring occasionally.
After 30 minutes, switch off the chicken pot. Once it's cooled down, take out the chicken pieces and shred them using two forks.
Do not discard the gravy in the pot.
Put the shredded chicken back into the pot, and cook further until it's reduced to a just moist consistency.
Add half teaspoon brown sugar to the onions, and continue frying. You can see them turning brown.
Onions will start to get caramelised now. Stir frequently so that they don't get burned. Cook till they are uniformly caramelised.
Toast the buns. Now let's start assembling the burger.
Add a layer of ketchup on the base.
Place the lettuce leaves followed by the tomato slices.
Place 1/4 of the shredded chicken on this.
Now add a generous helping of the mushroom puree on top of the chicken, followed by 1/4 of the caramelised onions.
Place the cap of the bun. Repeat for the remaining (three) buns. Serve your pulled chicken burgers hot and fresh!