Heat two tablespoons of the olive oil over medium-high heat in a medium saucepan and add the onion. Sauté until the onion is tender and lightly browned, about 4 minutes. Add the couscous and stir until the couscous begins to turn golden and smell toasty, about 4 to 5 minutes. Add the broth and water and salt to taste and bring to a boil. Reduce the heat, cover and simmer for about 15 minutes, or until the couscous is tender, and the liquid is absorbed. Line a rimmed baking sheet with aluminum foil, spray it with nonstick cooking spray (or a brush of oil), and spread the couscous out on the baking sheet to cool to room temperature.
While the couscous is cooking, make the shrimp. Fill a large bowl with ice water. Bring a large pot of water to a boil over high heat, and generously salt the water. Add the shrimp and cook for about 4 minutes until pink and cooked through. Drain the shrimp and transfer them to the ice bath. When they are cool, peel and devein the shrimp (leave the tails on if you like).
While the shrimp are cooling, make the dressing: combine 1 tablespoon of the remaining oil, rice vinegar, lemon juice, pesto, shallots, jalapeno, and salt and pepper in a container, and shake to combine.
Place the couscous in a shallow serving bowl and toss with the remaining tablespoon of olive oil, the artichoke hearts, and red pepper. Distribute the shrimp on top, and drizzle with the pesto dressing. Sprinkle over the chervil if using. Serve at cool room temperature.