Place the onion, tomatoes, vinegar, garlic, ginger, garam masala, turmeric, cumin, cinnamon, cayenne, honey, salt and pepper in a blender or food processor and process until smooth.
Place the olive oil in a large skillet over medium high heat.
Add the chicken and cook until well browned on all sides.
Add the potatoes and cook for about two minutes, stirring frequently.
Add the sauce to the pan and stir. Add the water.
Reduce the heat to low until the pot is simmering.
Cook, stirring occasionally, until the chicken and the potatoes are tender (about 40 minutes).
Sprinkle the cilantro over the top just before serving.
