Bring a large pot of well salted water to the boil, add rigatoni pasta and cook until just al dente. Reserve 2 cups of cooking water then drain pasta.
While the pasta is cooking make the sauce: In a large pan or pot heat 2 tbsp of olive oil over medium‐high heat. Add the vegan sausages and fry until golden brown on one side, then flip and cook until golden on the other side. Break up into small chunks and fry a little longer, then remove to a plate.
In the same pan heat another 2 tbsp of olive oil over low‐medium heat. Add the sliced garlic, chilli flakes and fennel seeds. Cook for a minute or two just until the garlic is fragrant but not coloured. Add in the chopped tomatoes. Throw in a good pinch of salt and a few cracks of pepper, along with the sugar if your tomatoes aren't particularly sweet, then allow to bubble away stirring occasionally until the tomatoes have broken down into a thick, sweet sauce (about 10–15 minutes). Remove from the heat.
Get a fry pan nice and hot, coat the pan with a couple of tbsp of olive oil then fry your diced eggplant in 2 or 3 batches, stirring them around often until they're nicely browned on all edges. Add more olive oil each time to coat the pan. As each batch is finished, add them to the pan with the cooked down tomatoes.
Once you've finished frying the eggplant, roughly chop most of the basil and add it to the sauce with the heat on low, along with the red wine vinegar and about a cup of the reserved pasta cooking water. Stir in the sausage chunks and the cooked pasta. Season to taste with salt and pepper. Add more vinegar if you think it needs it, as well as extra pasta cooking water if the sauce is too thick. Stir in the remaining whole basil leaves.
Once everything is warmed through, serve pasta with plenty of almond/cashew parmesan and an extra drizzle of olive oil.