Spinach and Feta Galette - Plenty

Ingredients

• 13.5 oz Plenty Baby Spinach
• 2 Tbsp unsalted butter
• 1 yellow onion, thinly sliced
• 4 cloves garlic, minced
• 4 oz creme fraiche
• 8 oz crumbled feta cheese, divided
• 2 oz parmesan cheese, finely grated
• 2 large egg yolk
• 1 tsp kosher salt
• 1 tsp freshly ground black pepper
• 1 frozen pie crust (defrosted)
• 1 large egg