Heat 1 1/2 teaspoons oil in a medium saucepan over medium-high heat. Add 1/2 cup onions and 1 tablespoon garlic; sauté 1 minute. Stir in barley, 1/4 cup cilantro, salt, black pepper, 1/2 cup broth, and jalapeños; bring to a boil. Cook 3 minutes or until liquid is nearly absorbed, stirring constantly. Add remaining broth, 1/2 cup at a time, stirring constantly until each portion is absorbed before adding the next (about 15 minutes).
Combine juice and next 5 ingredients (juice through curry paste); set aside.
Heat 1 1/2 teaspoons oil in a large nonstick skillet over medium-high heat. Add 1 cup onions, 1 tablespoon garlic, lemongrass, and ginger; sauté 1 minute. Add chicken, bell pepper, and peas; sauté 2 minutes. Stir in barley mixture, juice mixture, and milk; bring to a boil. Reduce heat; simmer 5 minutes or until sauce thickens, stirring occasionally. Stir in 1/4 cup cilantro. Sprinkle each serving with 1 teaspoon nuts.