Peel the sweet potatoes and chop into cubes. Cut the tempeh into cubes. Add the sweet potato and tempeh cubes into a bowl along with a one and a half tablespoons of oil. Toss to coat evenly.
Pre-heat an oven to 390 degrees and place some baking paper on a tray. Add the sweet potatoes and tempeh and cook for 20 minutes. Turn over half way through for even cooking.
Peel and chop the onion and garlic. Add some oil to a pot and cook the onions for around 4 minutes until they start to brown and then add the garlic. Cook for another minute.
Add the dried spices along with the ginger and tomato puree. Cook for another 30 seconds then add a pint of hot water along with the peanut butter. If the peanut butter is quite firm you can reserve some of the water and add the peanut butter to a jug along with the water. Then stir the water and peanut butter to reach a smooth consistency before adding to the pot.
Bring the pot to a boil stirring everything well and then reduce to a very gentle simmer.
Once cooked, add the sweet potatoes and tempeh. Stir the pot so everything is coated. Simmer for another five minutes or so to allow the flavors to absorb and the sauce to thicken.
Serve with some cooked rice and garnish with chopped cilantro leaves.