Shortbread Lemon Sheet Cake (Print Version)
# Ingredients:
→ Shortbread Base
01 -
3 cups crushed shortbread cookies (about 11-15oz blended into fine crumbs)
02 -
5 tablespoons melted unsalted butter
03 -
1 tiny pinch salt
→ Lemon Cake Mixture
04 -
1 tablespoon freshly grated lemon peel (roughly 1 lemon worth)
05 -
3/4 cup room temp buttermilk
06 -
2/3 cup room temp sour cream
07 -
3 whole eggs at room temp
08 -
1 egg white at room temp
09 -
1 tablespoon vanilla flavoring
10 -
1 teaspoon lemon flavoring (if you want)
11 -
1/3 cup veggie oil
12 -
1/4 cup plain flour
13 -
1 box (15.25oz) lemon cake mix (we like Duncan Hines)
→ Lemon Filling
14 -
3 egg yolks
15 -
1 whole egg
16 -
3/4 cup white sugar
17 -
1/2 cup fresh lemon juice
18 -
2 tablespoons grated lemon peel (about 2 lemons)
19 -
4 tablespoons unsalted butter
→ Lemon Frosting
20 -
1 1/2 cups barely softened unsalted butter
21 -
1 teaspoon lemon flavoring
22 -
1 tablespoon vanilla flavoring
23 -
1 tiny pinch salt
24 -
1/4 cup heavy cream
25 -
6-7 cups icing sugar
26 -
1 drop yellow food coloring gel
→ Garnish
27 -
1 cup broken shortbread cookie pieces
# Instructions:
01 -
Lightly grease a 9x13 baking pan with some shortening and dust it with flour so nothing sticks. Get your oven warming up to 325°F (165°C).
02 -
Turn shortbread cookies into fine crumbs using a food processor, then scoop 3 cups into a bowl. Mix in the melted butter and salt until everything's wet. Pack this mixture down firmly in your pan, using something flat like a measuring cup bottom to smooth it out.
03 -
Grab a big bowl and whisk together the lemon peel, buttermilk, sour cream, eggs, egg white, vanilla, lemon flavoring if you're using it, veggie oil, and flour. Sift the cake mix on top and stir gently just until it's all mixed.
04 -
Pour your batter right on top of the raw shortbread base. Stick it in the oven for 28-30 minutes or until you can poke it with a toothpick and it comes out clean. Let it cool completely in the pan before you do anything else.
05 -
While your cake's in the oven, mix egg yolks, whole egg, sugar, lemon juice, and peel in a medium pot over medium heat. Keep whisking as it gets thicker, about 6 minutes, until it coats your spoon. Take it off the heat and stir in butter chunks until they melt. Strain out the peel bits. Cover it with plastic wrap touching the surface and chill it fully.
06 -
Using your stand mixer with the paddle, beat butter for about a minute until it's fluffy. Throw in salt, flavorings, and heavy cream, mixing until they're blended. Add icing sugar bit by bit, about 1/2 cup at a time. Drop in the yellow coloring. Beat on high for a minute to get it fluffy, then slow it down for 30 seconds to work out air bubbles.
07 -
Spread most of your frosting evenly on the cooled cake. Save about 1 1/2 cups in a piping bag with a 1M tip. Pipe lines of frosting shells in rows. Add the cold lemon filling between these piped lines.
08 -
Scatter broken shortbread cookie bits all over the cake for crunch and extra shortbread flavor.
# Notes:
01 -
This treat blends the tangy zip of lemon bars with soft sheet cake texture
02 -
You can keep this cake in the fridge for up to 3 days if covered
03 -
Let the cake sit out a bit before eating for the best taste