Cut the peel and pith away from the oranges. Use a small, serrated knife to segment the orange, catching any juices in a bowl, then squeeze any excess juice from the off-cut pith into the bowl as well. Add the mustard, honey, vinegar, oil, and some seasoning to the bowl and mix well.
Using a vegetable peeler, peel carrot ribbons into the dressing bowl and toss gently. Heat a drizzle of oil in a frying pan and cook the halloumi for a few mins until golden on both sides. Toss the watercress through the dressed carrots. Arrange the watercress mixture on plates and top with the halloumi and oranges.
