Spinach and Cheese Quiche | Quiche Florentine

INGREDIENTS

For the crust:
• 2-1/2 cups (300 grams) all-purpose flour
• 1 teaspoon salt
• 1 teaspoon mixed herbs
• 170 g cold butter, cubed
• 1 egg yolk
• 6 tablespoons ice water

For the filling:
• 60 g butter, divided into 30 and 30 pieces
• 1/2 red onion, sliced
• 2 large garlic cloves
• 130 g fresh spinach
• 4 whole eggs
• 1/2 cup sour cream
• 1/2 cup whole milk
• 3/4 teaspoon salt
• 1/4 teaspoon black pepper
• 200 g grated cheese (I used cheddar, but you can use gouda, manchego, etc.)