1. Sprinkle 1 large grated cucumber with 1/2 tsp salt in a bowl and let stand for 10 to 15 minutes to draw out juice.
2. Place 2 cups greek yogurt into a separate bowl. dump the grated cucumber and its juice onto a sturdy, dry paper or cloth towel and squeeze as much moisture as possible from the cucumber. mix cucumber into yogurt.
3. Add 4 cloves of minced garlic, 1 pinch of cayenne pepper and juice of half a lemon. mix thoroughly.
4. Stir 2 tbsp chopped dill leaves and 1 tbsp chopped fresh mint leaves into yogurt-cucumber mixture. season with salt and black pepper. adjust all seasonings to taste.
5. Cover bowl with plastic wrap and refrigerate for 3 or 4 hours (or overnight). transfer to a serving bowl and garnish with a sprig of dill and a sprinkle of cayenne pepper for color.