Place orange juice in a small saucepan and bring to a boil over medium heat.

Reduce to a simmer and cook until the juice has reduced by half, about 15 minutes.

Set aside to cool, then mix with 3 tablespoons of the olive oil to make a dressing and set aside.

In a large saucepan, bring stock and 1 tablespoon oil to simmer.

Add quinoa, cover and simmer for 15 minutes.

Transfer the cooked quinoa to a large bowl to cool.

Add bell peppers, leeks, red onion, chives and mint and salt and stir to combine.

Season sablefish pieces with remaining 1/4 teaspoon salt and pepper.

Heat remaining 1 teaspoon oil in a large skillet over high heat.

Gently place fillet pieces, skin side down in pan.

Cook until the skin is crispy and golden brown, about 3 minutes.

Turn and cook until the fish is opaque and slightly firm, about 3 minutes.

Toss the mizuna with enough dressing to coat the leaves.

Evenly divide among four serving plates, then top with quinoa and fish. Drizzle with remaining dressing and serve immediately.