Throw the sweet potato into a mixing bowl along with the ground coriander, paprika, 1 tablespoon of the olive oil, salt and pepper. Spread onto a foil-lined baking tray and roast in the oven for 25–30 minutes until they are soft all the way through.
Meanwhile, heat the remaining olive oil in a small saucepan and cook the onion and garlic on a medium heat until softened and slightly browned. Throw in the black beans, coriander (stalks, leaves and all), red chilli and 80 ml water, stirring well. Bring to a simmer and cook for 10 minutes. Lightly crush the black beans with the back of a wooden spoon, take the pan off the heat and leave to one side.
For the salsa, simply blitz the pepper, chilli, red onion, cucumber, olive oil, lime juice and agave together in a food processor and season with salt and pepper to taste.You should have a tasty, bright green salsa with a good, thick consistency.
Check the sweet potatoes are cooked through and, if so, lightly crush with the back of a fork.
To build the nachos, simply spread the tortilla chips on a platter and load up with the spiced sweet potato, black beans and salsa, topping with a generous handful of freshly chopped coriander.