- 2 slices firm white sandwich bread, crusts removed
- 2 garlic cloves
- 1/2 cup pine nuts (2 1/2 ounces), toasted and cooled
- 1/2 cup walnuts (1 1/2 ounces), toasted and cooled
- 3 tablespoons fresh lemon juice, or to taste
- 1/2 cup extra-virgin olive oil
- 1/2 teaspoon salt
- 1/4 teaspoon black pepper
- 1 medium head cauliflower (about 2 1/2 pounds)
- 1/4 cup olive oil
- 3 tablespoons thinly sliced celery leaves (optional)
- Soak bread in a bowl of water 30 seconds, then squeeze dry and set aside.
- Drop garlic into a food processor with motor running, then drop in nuts and process until finely ground. Add bread and 3 tablespoons lemon juice and process until smooth. With motor still running, add oil in a slow, steady stream until incorporated. Transfer to a bowl, then stir in salt and pepper and lemon juice to taste.
- Remove any leaves from cauliflower, leaving core intact. Cut cauliflower into 1/2-inch-thick slices as if it were a loaf of bread, then cut slices into 2-inch pieces (some florets will separate).
- Bring cauliflower to a boil with enough water to cover it in a 4- to 5-quart pot, then reduce heat and simmer until just tender, 4 to 6 minutes. Drain well in a colander and pat dry.
- Heat 2 tablespoons oil in a 12-inch heavy skillet over moderately high heat until hot but not smoking, then sauté half of cauliflower, turning over occasionally, until very well browned on both sides, about 8 minutes total.
- Transfer to a platter with a slotted spatula and season with salt and pepper.
- Wipe out skillet, then sauté remaining cauliflower in remaining 2 tablespoons oil in same manner, transferring to platter and seasoning.
- Serve cauliflower, warm or at room temperature, with sauce and celery leaves (if using).