Chef Michael Anthony fortifies the deeply flavored broth for this dish with caramelized onions and kombu, an edible dried kelp commonly used in Japanese cooking.
- 3 tbsp. extra-virgin olive oil
- 5 onions, thinly sliced
- 3 shallots, thinly sliced
- 2 cloves garlic, crushed
- 2 leeks, white and light green parts only, thinly sliced on the diagonal
- Kosher salt and freshly ground black pepper, to taste
- 2 tbsp. sherry vinegar
- 1⁄4 cup madeira
- 6 cups vegetable stock
- 1⁄2 tsp. black peppercorns
- 3 small sprigs fresh thym
- 1 bay leaf
- 1 tbsp. white soy sauce
- 1 (1½″) piece ginger, peeled and thinly sliced
- 1 (5″) piece kombu
- 8 oz. spaghetti, preferably made with spelt
- 1 oz. shelled sea urchin (optional)
Heat 2 tbsp. oil in an 8-qt. pot over medium-high heat. Add onions, shallots, garlic, half the leeks, and ½ cup water, season with salt and pepper, and cook, stirring often (add a little more water, if necessary, to keep the onions from burning), until onion mixture is deeply caramelized, about 1 hour. Add vinegar; cook, stirring, until evaporated, about 3 minutes. Add madeira and repeat. Add stock, peppercorns, 1 sprig thyme, and bay leaf; bring to a boil. Reduce heat to medium-low; cook until mixture reduces by a third, about 1 hour. Remove pot from heat; add remaining thyme, soy, ginger, and kombu. Cover and let steep for 15 minutes. Set a fine strainer over a 3-qt. pot and strain broth, discarding solids; season with salt, set aside, and keep hot.
Meanwhile, bring a large pot of salted water to a boil. Add spaghetti and cook, stirring, until al dente, about 9 minutes. Drain spaghetti and divide between 4 deep, warm serving bowls. Heat remaining oil in a 12″ skillet over high heat. Add the remaining leeks and cook, flipping once, until the leeks are browned, about 4 minutes. Top spaghetti with leeks and ladle hot broth into each bowl. Garnish with sea urchin, if you like, and serve immediately.