Chill glass or china plates and salad forks in the freezer prior to making the salad.
Cut watermelon into 1 1/2 inch slices. Using a 2 inch cookie cutter, cut rounds out of the watermelon slices.
Place 2 watermelon rounds on each chilled salad plate and crumble over the feta, then sprinkle toasted pine nuts over the feta.
Drizzle over balsamic glaze, olive oil and season to taste with freshly ground black pepper. Garnish with spearmint sprig. Serve immediately.