Cut the tofu block into largish slabs--about 2 inches square. Heat two teaspoons of coconut oil in a wide, non-stick saucepan or a cast iron skillet large enough to hold the curry. Add the tofu slabs to the pan and fry each side until they develop a nice, golden crust. Remove the tofu cubes and place in a plate lined with a paper towel. When cool enough, cut each slab into smaller cubes.
Heat the remaining teaspoon of coconut oil in the same saucepan or skillet. Add the onions, add salt and pepper, and saute until soft but not brown. Add garlic to the pot and saute another minute.
Add the spices to the pot--turmeric, paprika and curry powder. Add the habanero or scotch bonnet pepper, thyme and bay leaf. Mix well.
Add three cups of water or vegetable stock to the pot. Add the potatoes and bring to a boil. Cover, lower heat until the liquid is bubbling gently, cover, and let the potatoes cook until soft, about 10 minutes.
Add salt to taste, then add the tofu cubes back into the curry. Bring to a boil and let it cook another five minutes.
Mix the cornstarch with ¼ cup water and whisk until smooth. Add the slurry to the curry and mix well. You will see the curry thicken. If you want a thinner curry, just skip the cornstarch slurry. Turn off heat and garnish with cilantro and scallions, or both.