Blueberry Cake Donut Bars + Iced Coffee Vanilla Bean Syrup

One of my favorite things about summer is that every weekend seems like a holiday. Even if you’re not traveling anywhere, Saturday and Sunday are an escape from the monotony of Monday through Friday. Sleeping in and having a leisurely brunch feels decadent—so much more so than any other season because the sunny weather is a paradise outside of your window.

Honestly brunch is the meal of summer. Just walk by any restaurant around midday, and you’ll find 30 people waiting for a table and a mimosa. Other than the excuse to drink alcohol in the bright daylight of the morning, my favorite thing about brunch is the special coffee and sweet treats.

Well I think I have the solution to recreating that weekend self-indulgence for your weekday breakfast. Blueberry cake donut bars and vanilla iced coffee. Yum. Blueberries sit pretty in a glazed, cinnamon-scented cake while vanilla accents the bitterness of a silky iced coffee.

Simple syrup creates the base of the vanilla bean syrup that your pour into any iced coffee of your choice. The simple syrup is an important trick to have in your repertoire as I’m sure you are well aware if you’ve ever tried putting sugar in a chilled beverage. Sugar needs heat to dissolve in water, so with cold drinks, you need to deliver it in an already-dissolved form! Simple syrup is classically equal parts sugar and water, boiled, and cooled. Once in water and heated, the sugar remains dissolved. The sugar molecules grab ahold of the water molecules when they’re heated up. At higher temperatures, water molecules move more quickly creating more space in between them. Sugar can then swoop in and fit in the crannies.

There’s something that is even cooler about simple syrup though. When you heat sugar in water at high temperatures, the sucrose molecules break down. Sucrose, composed of one fructose and one glucose, unlinks in the middle and becomes its principle parts. This is called an invert sugar. The fructose and glucose are sweeter apart than they are together. Pretty cool huh?

Simple syrup is not only useful for your iced coffee. It is abundant in mixed drinks and other beverages. So take this vanilla bean syrup as your jumping off point and then experiment all you want! Don’t skip out on the blueberry cake donut bars though. Trust me. They’re scrumptious.

Vanilla Bean Syrup

I love the recipe from How Sweet It Is (also one of my favorite blogs!)

She also has several other flavors you can try out in your coffee!

Blueberry Cake Donut Bars

Adapted from Food52

Serves 8

Donut Bars

½ cup butter, softened

1 cup sugar

2 ¼ cups all-purpose flour

2 teaspoons baking powder

¾ teaspoon baking soda

1 pinch salt

¼ teaspoon ground cinnamon

2 eggs

1 egg yolk

1 cup buttermilk (or 1 tablespoon vinegar in a measuring cup filled with milk to 1 cup)

1 teaspoon vanilla extract

1 pint blueberries, rinsed and dried


2 cups powdered sugar

3 tablespoons heavy cream

⅓ cup milk

¼ teaspoon lemon zest

1. Preheat your oven to 350⁰F. Beat the sugar and butter together in a large bowl until well-combined. This should be simple to do with a wooden spoon or rubber spatula.

2 In a separate bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon. And in another bowl, whisk the eggs, egg yolk, vanilla, and buttermilk together.

3. Add the dry and wet ingredients to the butter/sugar mixture alternately in 3 additions each. Mix until the ingredients are just combined.

4. Fold the blueberries into the batter and pour into a greased 9×9 inch cake pan. Bake for 25-30 minutes or until a toothpick comes out clean in the center. Cool and cut into 8 bars.

5. Whisk the ingredients for the glaze together. If the glaze is not sufficiently runny, add 1-2 tablespoons of extra milk to the mix.

6. If available, pour the glaze over the bars while on a wire rack. Otherwise pour over the bars on your plate and enjoy the runoff! Let set before you dig in.



  1. Ohhh yes! That’s really cool to hear about the science behind simple syrup. Fascinating. I love having homemade simple syrups for cocktails, but also for my iced coffees, which I drink year-round. I usually have like a minimum of 4 different simple syrups in the fridge and it drives Robert crazy. This blueberry donut cake looks amazing too!

    • Kelsey
      July 9

      Thanks Sara! Yes flavored syrups are just incredible! They make everything taste wonderful.

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