Salmon Wellington

Ingredients (13)

• 1 tablespoon unsalted butter
• 1/2 tablespoon Dijon mustard
• Zest of 1 small lemon about 3/4 teaspoon
• 3/4 teaspoon kosher salt divided
• 1/2 teaspoon black pepper divided
• 1/2 teaspoon dried thyme
• 2 teaspoons extra virgin olive oil
• 4 cups fresh baby spinach
• 2 cloves garlic minced
• 2 tablespoons freshly grated Parmesan cheese
• 1 large egg yolk plus 1 teaspoon water
• 1 sheet frozen puff pastry thawed in the refrigerator
• 2, 6- ounce salmon fillets skin removed