Coarsely grind the pistachios in a food processor, pulsing on and off. Add the mint, orange zest, crumbled feta, olive oil and pepper, and pulse to combine into a thick paste. Set aside.

Prepare the dressing: Whisk together the olive oil, balsamic syrup and mustard.

Peel the beets and cut them into rounds about 1/8-inch/3.2 mm. Place a half teaspoon of the feta mixture in the center of a serving plate. Place a beet round on top. Add a teaspoon of the feta mixture and top with a beet round. Continue until all the slices of the first beet are used up. The stack should end with a beet round. Drizzle with a little dressing, sprinkle with pink peppercorns, garnish with mint and serve. Repeat with remaining beets and feta mixture.