Cook the sweet potatoes, cut into cubes, either by steaming or roasting them in the oven with olive oil and salt. Allow them to cool.
Slice the apple into wedges or cubes, leaving the skin on for extra colour, and drizzle with lemon juice to prevent browning.
In a bowl, combine the salad mix, sweet potatoes, and apples, then dress with a simple lemon vinaigrette made with olive oil, salt, and pepper.
Finish with a sprinkle of poppy seeds.