Cook the pasta according to the package instruction.
Meanwhile, thinly slice the shallot & garlic, then heat the oil in a large frying pan and gently sauté them. Add the chilli too, if used. When translucent, add the kale and squeeze over the lemon juice. Put a lid on to allow the kale wilting.
Tear the mozzarella into small chunks.
When the pasta is ready, drain it, reserving a small cupful of the cooking water.
Add the pasta to the kale, together with the cheese bits and a drop of the cooking water.
Turn off the heat, and stir gently until the cheese has melted. Add more water, if the sauce is too dry.
Season to taste, then serve with the chopped nuts scattered on top.