Blueberry Crumb Bars

Ingredients.

Let’s take a look at what you need to make a batch of these berry bars. 

Oat Crust & Topping.

• Oats. Old-fashioned oats are my preference for these bars. They add a nice flavor and texture. Quick cook oats, which are flaky compared to old-fashioned, can be used. Blueberry bars made with quick cook oats are a smidgen more cake-like. But it that’s what you have on hand, don’t hesitate to use them. Don’t use steel cut oats. Those won’t work. If you’re gluten-free, use gluten-free oats. 
• Flour. All-purpose or gluten-free flour helps the bars hold together. 
• Sugar. Brown sugar adds a very subtle flavor to the crust. If you don’t have any in the house, use an equal amount of granulated sugar. 
• Cinnamon. Ground cinnamon adds a nice flavor. You can also use pumpkin pie spice. 
• Salt. Helps enhance all the flavors. Use table (fine) salt.
• Butter. A stick of cool butter is mixed into the oat-flour mixture. And cool is the key here. You want the butter to feel soft to the touch. This way it’s easy to mix into the other ingredients. 

Blueberry Filling.

• Blueberries. Fresh and frozen blueberries work in this recipe. If you use fresh blueberries, remove any stems and wash the berries before using them. For frozen blueberries, don’t let them thaw before using them. Simply use the blueberries from frozen. 
• Sugar. A little granulated sugar adds sweetness to the filling.
• Cornstarch. We need the filling to thicken and cornstarch is perfect for this. Since cornstarch needs to reach 212 to thicken, make sure the filling bubbles. That’s key. 
• Lemon Zest and Juice. A little lemon zest and juice really help to bring out the flavor in the blueberry filling. 

Step One: Make the Crust/Topping Mixture. 

The crust and topping are made from the same easy-to-make streusel mixture. To make it, whisk together the oats, flour, brown sugar, cinnamon, and salt. If there are any clumps of brown sugar, break them up with your hands. 

Add the soft butter. Do this with either your hands or a pastry cutter. When it’s mixed, you shouldn’t see any large pieces of butter left in the bowl. I like to test the mixture by giving it a squeeze. If it holds together easily, you’ve mixed it enough. If it falls apart or looks floury, keep mixing in the butter.

Remove about a cup of the mixture for the topping and set it aside. Press the remaining oat mix into a parchment-lined 8-inch square pan. It’s important to press the mixture firmly into the pan. This way, the crust won’t crumble apart when you cut the bars after they’re baked.

By the way, this streusel-like mix keeps great in the fridge. If you want, prepare it the night before you plan to bake. Just be sure to store it in a covered container to keep it from drying out. 

Step Two: Prepare the Filling and Assemble the Bars. 

The filling is so simple to put together. Start with washed and dried fresh blueberries or frozen blueberries. If they’re frozen, don’t let the berries thaw. They get too juicy and can make the bars soft.

Place the blueberries in a large bowl and add the sugar, cornstarch, lemon zest, and juice. Give this a good stir so that the blueberries are coated.

Spread the blueberries over the crust. Then sprinkle the reserved oat topping mixture all over the berries.

Step Three: Bake the Bars.

Place the pan into a preheated 350℉ oven. The bars take about 45 minutes to bake. Look for the topping to be light brown and the filling to bubble gently. 

When they first come out of the oven, they’ll be very delicate. If you try to cut them right away, they can fall apart. Let the bars cool in the pan. Once they’re cool, lift the parchment or foil overhang and remove the bars from the pan. Place the bars on a cutting board and cut into squares.