Heat olive oil in a skillet over medium heat. Sauté onion until lightly browned. Stir in garlic, curry powder, cinnamon, paprika, bay leaf, ginger, sugar and salt. Continue stirring for 2 minutes. Add chicken pieces, tomato paste, yogurt, and coconut milk. Bring to a boil, reduce heat, and simmer for 20 to 25 minutes. Remove bay leaf, and stir in lemon juice and cayenne pepper. Simmer 5 more minutes. Place atop an aromatic rice such as saffron, jasmine, or basmati or alternatively dice some potatoes and mix those in with the curry itself. Garnish with lots of fresh, chopped cilantro (if using) and serve.