In a small bowl, combine the ground coriander, ground cumin, turmeric, crushed fennel seeds, ground cinnamon, black pepper, ground mustard, and ground cloves. Mix well and set aside.
In a large skillet or saucepan, heat the olive oil over medium heat. Add the chopped onion and sauté for about 5 minutes, until the onions are translucent. Add the minced garlic and ginger, cooking for an additional minute until fragrant.
Stir in the prepared spice mixture, letting it cook with the onions, garlic, and ginger for about 1-2 minutes.
Add the diced chicken breasts to the pan, stirring to coat the pieces with the spice mixture. Cook for about 5-7 minutes, until the chicken is no longer pink on the outside.
Add the chicken broth and diced tomatoes to the skillet. Season with salt and cayenne pepper to taste. Bring the mixture to a gentle boil, then reduce the heat to low and let it simmer for 15-20 minutes.
If you prefer a thicker curry, mix the cornstarch with water in a small bowl to create a slurry. Stir this into the curry during the last few minutes of cooking.
Once the chicken is cooked and the curry has thickened to your liking, stir in the heavy cream. Let it simmer for an additional 5 minutes.
Sprinkle the chopped cilantro on top. Serve your chicken curry hot, paired with rice or your favorite bread.
