In the jar of a blender, combine the tomatoes, jalapeno, bell pepper, tomato paste, yogurt, xawaash, and salt and puree until smooth. Set aside.
Warm the oil in a large Dutch oven or other heavy pot set over medium heat. Add the onion, garlic, and ginger and cook, stirring occasionally, until just beginning to soften, about 5 minutes.
Sitr in the blended tomato mixture, bring the mixture to a boil, then immediately lower the heat, cover, and cook until very fragrant, about 10 minutes. This initial cooking forms the base of the sauce.
Stir in the potato, carrots, chicken, and coconut milk. Cover the pot and cook, uncovering it to stir occasionally, until the vegetables are tender, and the chicken is cooked through, about 30 minutes.
Season the stew to taste with salt. Serve hot, sprinkled with the cilantro, over cooked rice, and with bananas alongside (don't slice the bananas, just serve them whole and take a bite as you eat the stew).
Leftovers can be stored in an airtight container in the refrigerator for up to a few days and rewarmed in a heavy pot set over low heat (stir while you heat).