Cut the onion and bell pepper into cubes. Sauté with the mushroom slices in a pan over medium heat for 10 minutes.
While the vegetables cook, cut the chicken breast into cubes. Season with salt, white pepper, and paprika powder.
Heat oil in another pan over medium heat. Fry the seasoned chicken cubes for 5-8 minutes, stirring occasionally. Add the finely chopped garlic and fry for 1 more minute.
When the vegetables are translucent and tender, add them to the chicken. Stir in the tomato paste and mix well. Continue cooking over medium-low heat for 3 minutes.
Add some water, stir, and season with additional salt and pepper if needed. Simmer over medium-low heat for 10-15 minutes until the chicken reaches 74°C (165°F) internally.