Clean and trim the leeks, cut the fennel bulb into thin wedges and wash the mangetout.
Melt the butter in a heavy based pan and, when the butter has started to foam, add your leeks and fennel. Lower the heat and cook them gently for a few minutes until the leeks start to soften and the fennel is al dente.
Add the mangetout, increase the heat and ladle in the some chicken stock - about 2 ladel-fulls at a time. If you want to add thyme leaves now is the time to do it.
Allow the stock to almost evaporate before adding more. Do not stir the veg too much just give the pan a shake. When your happy with the texture of the vegetables allow the stock to reduce away, add some more butter, a few squeezes of lemon juice, loads of black pepper and just a little salt.
The vegetables are ready when the leek tops are soft but the bulb is still firm-ish, the fennel should still have a little bite and the mangetout should be al dente.
The extra knob of butter enriched the sauce and helps to adds a glaze to the dish.
Once finished serve immediately onto warmed plates
Have a great start to your week