Shrimp with Green Curry and Rice Noodles

• 1 cup chopped shallots (about 4)
• 2 fresh lemongrass stalks (optional), 1 or 2 outer leaves discarded and lower 6 inches of stalks thinly sliced
• 2 large garlic cloves, chopped
• 1 tablespoon chopped peeled fresh ginger
• 1 tablespoon finely chopped fresh cilantro stems
• 1 to 2 tablespoons bottled Asian green curry paste
• 11/2 teaspoons sugar
• 3/4 teaspoon salt
• 1/2 teaspoon turmeric
• 1/4 cup water
• 1/4 cup plus 2 tablespoons vegetable oil
• 1 (13- to 14-oz) can unsweetened coconut milk (not low-fat)
• 1 3/4 cups reduced-sodium chicken broth (14 fl oz)
• 3/4 lb dried flat 3/8-inch-wide rice noodles or 1/2 lb dried flat 1/8-inch-wide stir-fry rice noodles
• 11/2 lb peeled and deveined large shrimp (21 to 25 per lb)
• 2 to 3 teaspoons Asian fish sauce, or to taste

Purée shallots, lemongrass, garlic, ginger, and cilantro stems in a blender with curry paste, sugar, salt, turmeric, and water until as smooth as possible, about 1 minute.

Heat oil in a 4-quart wide heavy pot over moderate heat until hot but not smoking, then cook curry paste mixture, stirring frequently, until it just begins to stick to bottom of pot, 8 to 10 minutes. Add coconut milk and broth and simmer, uncovered, stirring occasionally, until reduced to about 3 2/3 cups, 8 to 10 minutes.

While sauce simmers, cook noodles in a 6-quart pot of boiling salted water, uncovered, stirring occasionally, until tender, 4 to 6 minutes. Drain in a colander and rinse under cold water. Drain noodles well and divide among 4 large bowls.

Add shrimp to sauce and simmer, stirring, until just cooked through, 2 to 3 minutes. Remove from heat and stir in fish sauce and salt and pepper to taste. Ladle shrimp and sauce over noodles.