Vegan autumnal pasta

This recipe was developed for us by north London vegan chef, Tantrem De Bastet. You can see more of his recipes on his site at www.vegandebastet.com. Follow him on instagram: @vegantantrem.
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Just what you need: an easy, comforting sauce with minimal ingredients. This can be accompanied by any combination of additional veg you happen to have. I've used some of my favourites for the perfect accompaniment here.
Ingredients
300g Sweet Potato or Pumpkin – peeled and chopped
2 tsp Vegetable Oil
1 Red Onion – sliced
1 Tbsp Cane Sugar
1 Tbsp Red Wine Vinegar
150 – 200g Pasta Water
2 Portobello Mushrooms – sliced
200g Chestnut Mushrooms – roughly chopped
150g Walnuts – roughly chopped
Pinch of Thyme
½ tsp Cayenne
1 Tbsp Maple Syrup
Pasta of choice – I use Mafaldine or Spaghetti
Method
Heat oven to 180C Fan and line a baking tray with baking paper.
Add the sweet potato and the vegetable oil to a bowl with a pinch of salt and black pepper and toss to coat.
Turn out the sweet potato onto the baking tray and bake for 40 minutes then set aside.
Cook pasta to package instructions and drain, reserving the water and return the pasta to the pot.
Add a Tbsp of oil to a sauté pan and heat until the oil is hot, add the onion with a pinch of salt and sauté until soft.
Add the sugar and vinegar and caramelise the onion.
Add the sweet potato, onion and 150g pasta water to a blender and puree to desired consistency, adding more pasta water if desired.
Pour the sauce onto the pasta and stir in to cover.
While blending the sauce, add a little oil to the sauté and fry the mushrooms for 6 minutes before adding a pinch of salt and pepper, cayenne and the thyme.
Add the walnuts and maple syrup and cook for 4 to five minutes.
Serve the pasta and top with the mushrooms and a drizzle of Olive Oil (optional)