half leeks lengthwise, rinse out dirt, and chop into thin half moons.
smash garlic cloves with a knife – chop if desired (I leave them whole).
chiffonade half the basil leaves, leave the others whole.
heat olive oil in a large skillet on medium to medium low, add leeks, and saute about 15 minutes, until almost caramelized .
add cauliflower, garlic cloves, walnuts and salt, sauté about 10 more minutes on medium.
create a small space in one side of the pan and add marmite, miso, and butter, breaking up miso and marmite into the butter as it melts together (don’t worry if it doesn’t quite mix together perfectly) Stir into the vegetable mixture. .
add tomato paste and whole basil leaves, stirring constantly to prevent any scorching, until the tomato paste has started to cook in the oil a bit, caramelizing at the edges and going from bright red to a deep red color. 2-5 minutes.
Take sauce off of heat. Bring a big pot of heavily salted water to a boil, and cook pasta to al dente .
reserve 1 1/2 cups pasta water before draining.
turn heat back on sauce pan to med-high and add pasta water to tomato sauce bit by bit until all is blended and reduced to a good consistency.
remove from heat, adjust salt of necessary, add fresh pepper, remove whole basil leaves and add the chiffonade basil leaves.