Preheat the broiler to high. Grease a baking sheet with olive oil.
In a large bowl, combine the cauliflower, 1/3 cup coconut milk, 2 cloves chopped garlic, 1 tablespoon grated ginger, and a pinch of salt. Let sit 10 minutes to "marinate". Spread the cauliflower in an even layer on the prepared baking sheet. Transfer to the oven and broil for 3-4 minutes, until the cauliflower is just beginning to char on the edges.
Meanwhile, heat the olive oil in a large skillet over medium heat. Add the onion and cook 5 minutes or until fragrant. Add the remaining garlic and ginger, cooking another 5 minutes.
Stir in the garam masala, curry powder, turmeric, and cayenne, and cook until fragrant, about 1 minute.
Add the tomato paste and remaining 2 cups coconut milk. Stir to combine, bring the sauce to a boil, cook 5 minutes or until the sauce thickens slightly. Stir in coconut oil. If the sauce seems thick, thin with 1/2 to 1/2 additional coconut milk or water.
Add the cauliflower and any juices on the pan and cook, stirring occasionally, until the sauce thickens slightly, about 5 minutes.
Serve the cauliflower and sauce over bowls of rice with fresh naan and mango chutney, if desired. Enjoy!