How to Make My Grandmother's Savory Passover Potato Pie

Ingredients

• 2 cups (240 g) all-purpose gluten-free flour
• 1 teaspoon salt
• 1/2 cup (115 g) unsalted butter, chilled and diced
• 1 large egg
• 3-4 tablespoons cold water
• 4 large potatoes (about 2 pounds or 900 g), peeled and grated
• 1 large onion, finely chopped
• 3 large eggs
• 1/4 cup (60 ml) heavy cream or non-dairy substitute
• 1/2 teaspoon black pepper
• 1 teaspoon paprika
• 2 tablespoons fresh parsley or dill, chopped (optional)