Tourte aux Pommes de Terre (French Potato Pie) | America's Test Kitchen

Ingredients

• 20 tablespoons (2½ sticks) unsalted butter , chilled, divided
• 2 1/2 cups (12½ ounces/354 grams) all-purpose flour , divided
• 1 teaspoon table salt
• 1/2 cup ice water
• 2 pounds Yukon Gold potatoes , peeled and sliced crosswise 1⁄8 inch thick
• 1/2 teaspoon baking soda
• 1 1/4 cups heavy cream
• 3 garlic cloves , minced
• 1 onion , halved and sliced thin
• 1 1/2 teaspoons table salt
• 1/2 teaspoon pepper
• 1/4 teaspoon ground nutmeg
• 2 tablespoons minced fresh parsley
• 1 egg , lightly beaten