Have your rice, couscous, quinoa or pasta ready before you start and keep warm
Heat the pot and add 1/2 the olive oil. Add the leek , garlic and anchovies and sweat till softened without colouring.
Turn up the heat a little and add the tomato, peas, ( chilli if using) and bring up to the boil add the Mussels (and a touch more oil if you love the taste). Put the lid on and simmer for 5 minutes on high ( or until you see a bit of steam escape. Then take off the heat and shake the pot and put the lid back on for 5-6 minutes.
All of the mussels should be open. Add the chopped herbs and serve .
A squirt of lemon is also nice with these