Take off the hat and bottom of each mushroom and set them aside to add, minced, to the leek fondue. Chop each foot into 4 scallop-size chunks. Criss-cross the tops and bottoms of each one with a knife. Marinate in the tsuyu sauce for 45 minutes.
Add the peas and cardamom pods to a pan with a big quantity of cold water, bring to the boil and simmer on medium heat, covered, for 40 minutes.
Chop the leek and shallots. In a large pan, sauté in the melted butter, on medium heat, covered, for 20 minutes. Season son salt and pepper, add white wine, mustard and lemon juice, and cook for another 20 minutes.
Grill your mushroom scallops in the olive oil for about 5 minutes.
Take the cardamom pods away, drain the peas and dress your plate!