Melt 2 tablespoons butter in a large skillet over medium-high heat. When the foaming subsides, add the couscous and cook, stirring frequently with a heatproof rubber spatula or wooden spoon, until some grains are just beginning to brown, about 3 minutes. Scrape the grains from the skillet into a large bowl and return the pan to medium heat.
. Add the remaining 2 tablespoons butter to the empty pan. Once the butter melts, add the onion, carrots, and 1 teaspoon salt. Cook, stirring occasionally, until the onion softens and begins to brown, about 5 minutes. Stir in the garlic, coriander, and ginger and cook until fragrant, about 30 seconds. Add the chickpeas, broth, and 2 cups water, increase the heat to medium-high, and bring to a boil.
Stir in the peas and pour the mixture over the toasted couscous; cover tightly with plastic wrap and allow to sit for 12 minutes. Remove the plastic wrap, add the herbs, and fluff the grains with a fork. Adjust the seasonings with salt and pepper to taste. Serve immediately, accompanied by lemon wedges.