In a medium pan, cook your pasta following packet instructions.
In a small saucepan, melt the butter (or spread) and Marmite over a medium heat. Add in the spinach until just wilted and set aside. Whizz the breadcrumbs in a food processor with the dried mushrooms and lemon zest. Spread evenly onto a baking tray and toast in the oven or under the grill until golden brown.
Once the pasta is cooked, drain, keeping a ladleful of the pasta water. Add the ladleful of pasta water into the Marmite butter sauce and stir to combine. Then add in the pasta and mix well until it is covered in the silky-smooth sauce.
Transfer to a plate and serve with a large sprinkle of the breadcrumbs. Finish with a sprinkle of parmesan and lemon juice.
Instead of dried mushrooms you can also use finely chopped fresh mushrooms.