Heat the olive oil in a deep skillet over medium heat. Add the onion and season with a generous amount of salt and black pepper. Cook for 5-6 minutes or until the onions are fragrant and tender. Add the crushed garlic and cook for an additional minute. Stir in the tomato paste and curry paste. Continue stirring until the pastes darken, about 2-3 minutes. Whisk in the coconut milk, chicken broth and granulated sugar. Bring the broth to a low boil, and then reduce to a simmer. Cook for an additional 20 minutes or until the flavors have melded and the broth has reduced. Adjust seasoning to taste.