4 large garlic cloves
1 medium zucchini
3/4 cup packed fresh basil leaves
1/4 cup packed fresh flat-leafed parsley leaves
1/2 cup water
2 tsp. fresh lemon juice

Preheat oven to 425F. Wrap garlic cloves tightly in foil. Cut zucchini into 1/4-inch-thick slices and season with salt and pepper. Put foil-wrapped garlic and zucchini on a baking sheet and roast in middle of oven until garlic is tender and zucchini is pale golden, about 15 minutes. Unwrap garlic and cool. Have ready a bowl of ice water. In a saucepan of boiling water blanch basil and parsley 10 seconds and drain in a sieve. Refresh herbs in ice water to stop cooking and drain in sieve. Sauce ingredients may be prepared up to this point 1 day ahead and kept separately, covered and chilled. In a blender blend garlic, zucchini, herbs, water, and lemon juice until smooth, about 1 minute, and season with pepper.