How to Make It
In a medium saucepan, heat 1 tablespoon of the oil until shimmering. Add the onion and cook over moderate heat, stirring occasionally, until softened and just starting to brown, about 5 minutes. Add the jalapeño, garlic and ginger and cook until fragrant, 1 minute. Add the peanut butter and red curry paste and cook over moderately low heat, stirring, until smooth, about 2 minutes. Whisk in the coconut milk, chicken stock, soy sauce and sugar and simmer until thickened slightly, about 3 minutes. Remove from the heat. Whisk in the lime juice and season with salt; let cool completely.
Meanwhile, in a large pot of salted boiling water, cook the soba noodles until al dente, about 5 minutes. Drain and rinse under cold running water until cooled. Shake out the excess water and blot the soba dry. Transfer the noodles to a large bowl and toss with the remaining 1/2 tablespoon of oil. Add the spicy peanut dressing and toss well to coat thoroughly. Add the carrots and cucumber and toss again. Garnish the soba with the lime zest and cilantro and serve.