Black Sea Bass with Sweet Parsnips, Arrowleaf Spinach, and Saffron—Vanilla Sauce from The French Lau

Ingredients

• 1 cup crisp, dry white wine, preferably Sauvignon Blanc
• 10 tablespoons (5 ounces) unsalted butter, cut into 8 pieces
• Six 2- by 3-inch pieces black sea bass fillet, (about 6 ounces each) skin on (see Crisping Skin)
• 2 large cloves garlic, peeled
• Reserved 1 cup mussel stock (from above)
• Three 2-inch strips orange zest (removed with a vegetable peeler)
• ¼ teaspoon saffron threads
• Pinch of kosher salt
• Kosher salt and freshly ground white pepper
• 2 bay leaves
• ¾ teaspoon olive oil
• 2 parsnips (about 5 ounces), peeled
• 2 teaspoons unsalted butter
• ½ vanilla bean, split
• ½ cup water
• 1½ teaspoons heavy cream
• 4 sprigs thyme
• 1 cup plus 1 tablespoon heavy cream
• 6 ounces spinach, washed and tough stems removed
• 1 teaspoon unsalted butter
• Kosher salt
• Canola oil
• 18 mussels, scrubbed and debearded
• 1 large shallot, peeled