With layers of shortbread cookie crust, cloud-like lemon mousse, and tart lemon curd, this pie is both light and bright, and a great way to celebrate the upcoming arrival of spring.

Lemon Mousse Pie with Shortbread Crust from completelydelicious.com

Happy Pi (Pie) Day!

I’ve been saving this onesie just for today:


I haven’t always been on the Pi Day = Pie Day bandwagon, but this year I decided to hop on board. Why not? I always need another excuse to bake a pie.

Lemon Mousse Pie with Shortbread Crust from completelydelicious.com

But what pie would I share with you? Since we’re still a few weeks out from spring produce I decided against a fresh fruit pie. But I still wanted something that tastes like almost spring and just hold on a little longer. And that for me, is lemon. It’s light and bright, and the perfect accompaniment to warmer weather and longer days.

Lemon Mousse Pie with Shortbread Crust from completelydelicious.com

This recipe is a little fussy, I will admit that, although I did make quite a few changes from the original to make it easier. It starts with a tart lemon curd, and add to that gelatin, whipped egg whites, and whipped cream. And voila, you have yourself a lemon mousse that is downright heavenly.

The mousse is sandwiched between a crust of shortbread cookie crumbs and a lid of lemon curd. One bite and the memory of all that fuss will be gone. Totally worth it, I promise.

Lemon Mousse Pie with Shortbread Crust from completelydelicious.com

A few notes about this recipe:

>>The gelatin in this pie helps it firm up for easy and pretty slicing. If you are okay with a softer mousse and messier slices, feel free to omit this step.

>>If you’d rather, graham crackers make a fine substitution for shortbread cookies in the crust.

>>To make the cookie crumbs for the crust, place the cookies (or graham crackers) in a zipped plastic bag and crush with a rolling pin. Alternately, you can use a food processor.

>>If you’re new to the term “fold”, it is a method of gently incorporating egg whites into other ingredients without deflating them. This video shows you how to do it.

>>This recipe contains raw egg whites, as do all traditional mousse recipes. So are raw egg whites safe to eat? Well, salmonella can be found in 1 of 20,000 eggs so the risk is very small. However, if you’d rather avoid them, look into using pasteurized egg white substitutes or powdered egg whites. I have tried neither, so unfortunately I cannot say how well they will work in this recipe.

Lemon Mousse Pie with Shortbread Crust from completelydelicious.com

4.41 from 5 reviews

Lemon Mousse Pie

Servings: 12 servings
Prep Time: 30 minutes
Cook Time: 20 minutes
Chill Time: 3 hours
Total Time: 3 hours 50 minutes
A light lemon mousse pie with shortbread crust and lemon curd topping.



  • 3 cups shortbread cookies , crushed (see Notes) (about 300 grams)
  • ¼ cup unsalted butter , melted (56 grams)

Lemon Curd:

  • ½ cup unsalted butter (113 grams)
  • 1 cup granulated sugar (200 grams)
  • 1 cup freshly squeezed lemon juice (235 grams)
  • 4 large eggs
  • 4 large egg yolks
  • ¼ cup cornstarch (28 grams)

Mousse filling:

  • 3 tablespoons water
  • 2 teaspoons gelatin (1 envelope)
  • Lemon curd , see above
  • 4 large egg whites
  • ½ cup granulated sugar (100 grams)
  • 1 cup heavy cream (237 ml)


To make the crust:

  • Combine the shortbread cookie crumbs and butter. Press into an ungreased 9-inch pie dish. Bake at 350°F for 10 minutes. Let cool completely.

To make the lemon curd:

  • Combine the butter, sugar, and lemon juice in a medium saucepan over medium low heat. Stir to dissolve the sugar and melt butter. Heat until steaming, but not quite yet boiling.
  • Meanwhile, whisk together the eggs and egg yolks with the cornstarch in a medium bowl. Slowly add the heated lemon juice mixture to the eggs in a slow and steady stream while whisking constantly. When fully combined, pour the mixture back into the saucepan.
  • Place saucepan over medium heat and cook until mixture thickens, about 5 minutes, while whisking constantly. Pass lemon curd through a fine mesh strainer (to remove any lumps) into a small bowl or container. Place plastic wrap directly onto the surface of the curd and chill in the fridge for at least 1 hour. Lemon curd may be stored in the fridge for up to 1 week.

To make the mousse:

  • Place the water in a small saucepan and sprinkle with the gelatin. Let sit for 5 minutes until gelatin is absorbed. Place over low heat and stir until gelatin is completely dissolved. Add ½ cup of the lemon curd and stir until mixture is smooth and all lumps are gone. Remove from heat and stir in another 1 cup of the lemon curd.
  • In the bowl of a stand mixer fitted with a whisk attachment, or in a bowl with a hand-held mixer, beat the egg whites on high speed until foamy. With mixer on, slowly add sugar. Beat to stiff peaks. Gently fold the egg whites into the lemon curd mixture in 3 additions.
  • Using the same bowl and whisk, beat the heavy cream on high speed to stiff peaks. Gently fold the whipped cream into the lemon mixture in 3 additions, careful not to deflate the mousse.
  • Dump the mousse into the prepared pie crust and smooth the top. Spread the remaining lemon curd (should be about ½ cup) on top of the mousse. Chill in the fridge for at least 2 hours. Garnish with whipped cream and lemons before serving, if desired. Store leftovers in the fridge for up to 3 days.


Note: Graham crackers may be substituted for the shortbread cookies, if desired.
Recipe adapted from Bon Appetit via Epicurious.
Calories: 339kcal, Carbohydrates: 31g, Protein: 5g, Fat: 22g, Saturated Fat: 13g, Cholesterol: 178mg, Sodium: 62mg, Potassium: 79mg, Fiber: 1g, Sugar: 26g, Vitamin A: 812IU, Vitamin C: 8mg, Calcium: 33mg, Iron: 1mg
Cuisine: American
Course: Dessert
Author: Annalise Sandberg
Have you tried this recipe?I’d love to hear about it! Leave a rating and review below, or take a photo and tag it on Instagram @completelydelicious with #completelydelicious.