Peel and finely grate the garlic and fresh ginger.

Remove the seeds from the sweet pepper and finely chop it.

Combine the garlic, ginger, sweet pepper, black pepper, salt, mustard, lemon juice, chili powder, and white vinegar in the large mixing bowl.

Add the 4 chicken thighs to the marinade and coat them thoroughly.

Cover the bowl and marinate the chicken in the refrigerator for at least 60 min.

Peel the 2 yellow onions and slice them thinly.

Heat the sunflower oil in a large deep pan over medium-high heat.

Brown the marinated chicken thighs for about 4 min per side.

Transfer the browned chicken thighs from the pan to a plate.

Cook the sliced yellow onions in the same pan until soft and lightly golden, about 12 min.

Stir the remaining marinade and 150 ml water into the softened onions.

Add the bay leaf and return the browned chicken thighs to the pan.

Cover the pan and simmer until the chicken is tender and reaches 74°C / 165°F internally, about 25 min.

Remove the bay leaf and serve the chicken with the onion sauce.