Bring a large saucepan of salted water to a boil and have ready a large bowl of ice and cold water. Trim haricots verts to 3-inch lengths and blanch in boiling water 2 minutes. Transfer beans with a slotted spoon to ice water to stop cooking and drain in a colander. In same boiling water cook onions 5 minutes and with slotted spoon transfer to colander to drain. In same boiling water simmer potatoes 7 minutes, or until tender, and drain in colander. Peel and halve onions and transfer to a bowl. Vegetables may be prepared up to this point 1 day ahead, cooled completely, and chilled in a sealable plastic bag.
Halve shiitakes if large. In a large heavy skillet heat butter over moderate heat until foam subsides and cook shiitakes with salt to taste, stirring occasionally, 2 minutes, or until just tender. Add peas and cook 2 minutes, or until bright green. Add beans, onions, and potatoes and cook, stirring occasionally, until just heated through. Stir in chives and season with salt and pepper and lemon zest and juice.
Recipe courtesy of Gourmet magazine