Preheat oven to 450°.
Place 1/2 shelled unsalted pistachios on a pan; bake for 4 minutes. Cool slightly and chop finely. Place 2 tbsp olive oil and 2 minced cloves of garlic in a small skillet over medium heat; cook for 3 minutes or until garlic begins to sizzle. Remove pan from heat; stir in pistachios, 1/2 tsp grated orange rind, 2 tsp fresh orange juice, and 1/4 tsp salt.
Heat a large skillet to medium heat. Add 1 tbsp olive oil to pan; swirl to coat. Score skin of each fillet with 3 diagonal (1/4-inch-deep) cuts. Combine 1/2 tsp salt, 1 tbsp fresh thyme, and 1/2 tsp ground mace in a small bowl.
Sprinkle flesh side of fillets with spice mixture. Add fill ets to pan, skin side down; cook 5 minutes or until desired degree of doneness.