Summer Berry Custard Bars

Custard bars with summer berries-yeah, this one will see a few more forms as I play with different fillings. For now think soft and creamy custard center injected with bright berries for a punch of fruitiness that’s crusted with Christina Tosi’s famous cake mix crust.

Summer Berry Custard Bars by Bakers Royale1

Summer Berry Custard Bars

Remember when I made Momofuku’s Ooey GooeyButter Cake Bars, but added blueberries to it to cut the sweetness? Of course the original recipe is great as is, but for my own preference, I wanted something little less sweet and a little more firm without having to freeze it. So for this recipe I started with the crust, but went with my own recipe for the filling.

Summer Berry Custard Bars via Bakers Roayle1
To start off I bypassed the cream cheese for sour cream to lighten things. And in keeping with the goal to tone down the sweetness I dropped the sugar ratio. I changed out the pound of powdered sugar for 1 ¼ cup of sugar and threw in a little cornstarch to make up for the loss of that in powdered sugar to help set the custard. Then of course I finished custard bar recipe with lots of berries, which of course had one of my co-workers calling this a custard pie bar—she might be right, but it seems too wordy.

Summer Berry Custard Bars by Bakers Royale 210x260

this recipe

Summer Berry Custard Bars

Yield: Makes 1 9x13 cake



  • 1 box of yellow cake mix
  • 4 ounces butter, melted
  • 1 egg
  • 1 tablespoon lemon zest

Berry Custard Filling

  • 3 large eggs
  • 1 1/4 cup sugar
  • 3/4 cups sour cream
  • 1/2 cup flour plus 2 tablespoons
  • 3 tablespoons cornstarch
  • 12 oz raspberries
  • 4 oz berries
  • 1 tablespoon lemon zest



Heat oven to 350 degrees F and line 9x13 pan with foil and cover with bake spray.

To make crust

Place the dry cake mix, butter, 1 egg and lemon zest in a bowl and mix until well blended. Press mixture into parchment-lined 9x13 inch pan. Set aside.

To make berry custard filling

  1. Place egg in a bowl of stand mixer fitted with a whisk attachment. Beat eggs until well combined. Add in sugar and beat and until foamy. Add in sour cream, flour, cornstarch and mix to combine. Turn off mixer and fold in raspberries, blueberries and lemon zest.
  2. Pour mixture on top of crust and bake at 350 degrees for 40-55 minutes or until the edges are a light golden brown, and the center slightly jiggles when pan is tapped.
  3. Cool completely in pan. Turn out onto a cutting board and cut into squares.

A few notes:

  • Note the crust recipe is minimally adapted by my addition of the lemon zest to balance the sweetness.
  • I used frozen berries, so keep in mind the coldness of the berries will immediately thicken the mixture as it comes in contact with the cornstarch. And of course any berries will work, so use what you prefer.
  • The custard bars are best served warm. To reheat, place sliced bars in the microwave for 30 seconds.

Crust (adapted from Christina Tosi's).

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  1. Avatar for Naomi Robinson says

    I am trying these this weekend for a dinner party. Will be using blackberries only and will let you know how they turn out.

  2. Avatar for Naomi Robinson says

    I always forget powdered sugar has corn starch. Thanks for the reminder :)

    I really enjoy all of your food photography (because it’s so moody), but I’m especially enjoying today’s bright photos. So fun & summery :)

  3. Avatar for Naomi Robinson says

    Do you think I could make this using only blueberries?

    • Avatar for Naomi Robinson

      Naomi replied: — July 23rd, 2012 @ 5:54 am

      Mimi- Absolutely! Blueberries will work just fine.

  4. Avatar for Naomi RobinsonMimi says

    Thanks for this recipe. It looks fabulous!

    I have two questions–are the measurements for the berries by weight or volume, and how do you think sliced strawberries would so in this recipe? Do you think they might be too watery/bleedy?

  5. Avatar for Naomi RobinsonCheryl says

    In the picture it appears you have sprinkled sugar over bar. Would you let me know if it was for the picture or part of the recipe?

    • Avatar for Naomi Robinson

      Naomi replied: — July 23rd, 2012 @ 5:54 am

      Cheryl-There is a slight dusting of confectioner sugar. It’s optional.

  6. Avatar for Naomi Robinson says

    I came into your post a few days ago, then I realized I have to bake the cake for my birthday, and bring it on a small beach on the Arno River in Florence where I’ll meet my friends to celebrate.. nothing better than custard bars to be wrapped and ‘delivered’ to everyone! I’ll bake something like this!! Thank you for the inspiration!

  7. Avatar for Naomi Robinson says

    Naomi, thanks so much for this recipe! I had about one spare hour in my busy week to make a birthday cake for my mom and I immediately came to these bars… so simple and everyone loved them! — even after a birthday dinner out, everyone went for second slices. Really delicious, and very pretty. I’ll definitely make them again!

  8. Avatar for Naomi RobinsonShannon says

    Wondering if you meant for the pan to be lined with foil or parchment? You have foil listed in one spot, parchment in another?

  9. Avatar for Naomi RobinsonCoco says

    This looks delicious with just one exception, the yellow cake mix. I don’t use anything processed, do you have a from scratch recipe??