Rinse the buckwheat thoroughly. Tip into a pan and toast for 5 mins, stirring till it smells nutty. Remove from the heat and leave to cool slightly. Pour in 300ml boiling water and place back on the heat. Simmer for 12-15 mins till the buckwheat is tender but with a slight bite. Drain.
While the buckwheat is cooking, peel and thinly slice the onions. Thickly slice the chestnut and portobello mushrooms. Peel and grate the garlic cloves, placing half into a bowl for later.
Set a frying pan on the heat for a couple of mins. When warm, drizzle in 1 tbsp olive oil. Add the mushrooms and sliced onions. Cook for 5 mins, stirring now and then.
While the mushrooms are cooking, zest and juice the lemon into the bowl with the garlic. Finely chop the parsley stalks and leaves and add to the bowl. Add 2 tbsp olive oil and a large pinch of salt and pepper. Mix well. This is your gremolata.
Finely slice the kale leaves and stalks. Finely chop the chilli, removing the seeds (the chillis this week are still super spicy without). Add the garlic and chilli to the pan with the mushrooms and stir. Add the kale and cook for 2 mins till the kale has wilted slightly and the mushrooms are soft.
Stir 1 tbsp of the gremolata through the drained buckwheat. Spoon into warm bowls. Top with the mushrooms and kale. Drizzle over the gremolata for plenty of zing.