Preheat your oven to 400°F and line a baking sheet with parchment paper.
Peel and cube the sweet potato into bite-sized pieces, then toss with half a teaspoon of the olive oil and a pinch of salt.
Roast the sweet potato cubes for 20-25 minutes until they are tender and slightly caramelized on the edges.
Season the chicken breast with sea salt and cracked black pepper, then grill over medium-high heat for 6-7 minutes per side until fully cooked.
While the chicken and potatoes cook, whisk together the remaining olive oil, lemon juice, and Dijon mustard in a small bowl to create the dressing.
In a large salad bowl, combine the mixed greens, sliced cucumber, and halved cherry tomatoes.
Slice the grilled chicken into strips and add them to the salad along with the roasted sweet potatoes.
Drizzle the lemon-Dijon dressing over the salad and toss gently before serving.