Slice the onion thinly and remove the core. Slice the mushrooms thinly.

Cut the chicken thigh into bite-sized pieces.

Heat olive oil in a pan over medium heat. Add chicken and cook until the color changes. Add onion and mushrooms, and sauté until the onion softens and the chicken is cooked through.

Add demi-glace sauce, water, and a pinch of salt and pepper. Stir and heat on low until the sauce becomes smooth.