Grandma Betty swore this was her 4 ingredient secret weapon. I finally made it myself and the whole pan was gone before dinner finished.

For a lighter texture, you can fold in up to an additional 1/2 cup of whipped cream into the lemon pudding filling before pouring it into the crust, which makes the pie extra airy. If you prefer a stronger lemon flavor, whisk in 1 to 2 teaspoons of fresh lemon juice or a little lemon zest into the pudding mixture before folding in the whipped cream (just know this is technically an extra ingredient beyond the core four). To keep it classic and easy, stick with the four main ingredients but feel free to garnish the finished pie with very thin lemon slices or a light sprinkle of graham cracker crumbs right before serving. For a slightly firmer pie that travels well to potlucks, reduce the milk to 2 1/2 cups total so the filling sets more firmly. If you need to make this ahead, the pie can be covered and refrigerated for up to 24 hours before serving; add any garnishes just before slicing. Food safety tips: Always use cold milk and keep the whipped cream refrigerated until you’re ready to mix. If you’re using frozen whipped topping, make sure it’s fully thawed in the fridge (not on the counter) before folding it in. Store any leftover pie covered in the refrigerator and enjoy within 2 to 3 days for best quality. Do not leave the pie out at room temperature for more than 2 hours, especially in warm weather, since the dairy-based filling and whipped cream need to stay chilled.