Mix watercress with arugula, arrange on plates. Pears cut into thin slices, sprinkle with lemon juice (so as not to darken), put on top of the leaves.
Stuff each date with half a walnut and put 2 pieces on a plate. Mix the olive oil with the vinegar and pour this dressing over the salad.
Slice the cheese very thinly (you can use a paring knife for this) and sprinkle on top.