Seasonal Fruit Crumble Bars

1. Preheat the Oven

Preheat your oven to 350°F (180°C) and adjust the oven rack to the lower-middle position. Line an 8- by 8-inch square, anodized aluminum pan with two long strips of parchment paper, ensuring the bottom and sides are covered. Crease the parchment as needed to fit snugly.

2. Prepare the Dry Mix

In a large bowl, combine the rolled oats, all-purpose flour, light brown sugar, baking powder, kosher salt, baking soda, and ground cinnamon. This dry mix can be prepared ahead and stored in a bag at room temperature if needed.

3. Add the Butter

Add the cold, unsalted butter cubes to the bowl. Toss them in the dry mixture to coat, then use your fingers to smash each cube flat. Continue this process until the mixture resembles a clumpy, streusel-like texture. The butter should mostly disappear into the mix, creating a flaky texture perfect for crumble bars.

4. Form the Dough

Add the cold egg to the mixture and stir with a flexible spatula until a soft dough forms. Scatter about two-thirds of this dough (approximately 16 ounces or 455g) into the prepared pan, gently pressing it into an even layer. Aim to press the dough so it forms a cohesive base without compressing it too much.

5. Prepare the Filling

For the filling, spread your choice of jam or scatter the juicy fruit evenly over the dough. Sprinkle the filling with a pinch of salt and a squeeze of lemon juice to enhance the flavor.

6. Add the Topping

Crumble the remaining dough mixture on top of the filling, resembling a streusel topping. Bake the bars in the preheated oven for about 45 minutes, or until they are puffed, firm, and golden brown. This golden brown color indicates that the bars have baked to the right texture.

7. Cool and Slice

Allow the bars to cool in the pan to room temperature. Once cooled, gently loosen the sides with a dull knife and transfer the bars to a cutting board. Cut into pieces as desired.

8. Serve

Serve the crumble bars with a dollop of whipped cream or enjoy them plain. Store any leftovers tightly wrapped in plastic at cool room temperature for up to 3-4 days. Enjoy your delightful Seasonal Fruit Crumble Bars, a treat that's perfect for any time of the year!