Halve or quarter the red chilli pepper and remove the white seeds and partitions. Rinse. Finely chop the chilli. Halve or quarter the yellow bell pepper and red pepper, remove seeds and partitions, rinse, and cut into cubes. Clean the spring onions and cut into rings. Peel and mince the garlic clove. Rinse the chicken fillet, pat dry, and cut into strips.
Heat the oil in a wok or large pan over medium-high heat. Add the spring onion rings and fry for 2 minutes. Add the chicken strips and fry for 3-4 minutes until the chicken is cooked through (internal temperature 74°C / 165°F). Add the chopped chilli and diced peppers, and stir-fry for 3 minutes. Add the minced garlic and fry for 1 minute. In a bowl, mix together the tomato paste, peanut butter, and chicken broth. Pour this mixture into the pan and bring to a simmer over medium heat. Simmer for 5-7 minutes until the mixture thickens slightly. Season with salt and pepper to taste.