Heat sesame oil in a large skillet over medium heat; cook and stir onion until it turns translucent, about 5 minutes. Stir in garlic and cook until garlic starts to brown, about 5 to 8 more minutes.
Mix in the lentils and cook 3 to 4 minutes to blend flavors, stirring lightly. Stir carrots and corn kernels into the mixture. Reduce heat to low.
Pour in 2 tablespoons white wine and 2 tablespoons chicken broth; let the mixture simmer, stirring occasionally.
Bring 2 cups chicken broth and 1/4 cup white wine to a boil in a saucepan; stir in couscous and reduce heat to low. Simmer couscous until the liquid has been absorbed and the couscous pearls are tender, about 8 minutes.
Stir 2 more tablespoons each of chicken broth and white wine into lentil mixture and lightly toss baby spinach leaves into the vegetables in the skillet until wilted, about 5 minutes.
Transfer cooked couscous to a serving bowl and gently stir the spinach-lentil mixture into couscous until thoroughly combined.
Drizzle with lemon juice, sprinkle with black pepper, and lightly stir again.
