Ingredients
Equipment
Method
- First, preheat your oven to 350°F (177°C). Line the bottom and sides of a 9×13-inch baking pan with parchment paper, leaving an overhang to create a "sling" for easy lifting. Set aside.
- In a large bowl, whisk together the flour, granulated sugar, brown sugar, baking powder, cinnamon (if using), and salt until well combined. Add the cold, cubed butter.
- Using a pastry cutter, two forks, or a food processor, cut in the butter until the mixture resembles pea-sized crumbles and all flour is coated. This may take at least 5 minutes with a pastry cutter.
- In a separate, smaller bowl, whisk together the egg, milk, and vanilla extract until fully blended. Pour this wet mixture over the flour and butter crumbles. Gently mix until the mixture resembles moist, crumbly sand; use your hands if needed.
- You should have about 6 cups of crumb mixture. Set aside exactly 2 cups for the topping. Press the remaining crumb mixture into the bottom of your prepared pan to form the crust, flattening it evenly with your hands or a flat spatula. Set aside.
- Next, prepare the filling: In a medium bowl, gently mix the chopped strawberries, sliced rhubarb, cornstarch, and orange zest (if using) until just combined.
- Carefully spread the fruit filling over the pressed crust in the baking pan. Sprinkle the reserved 2 cups of crumb mixture over the fruit filling. If using, sprinkle the old-fashioned oats over the crumb topping.
- Lightly press the topping down with the back of a large spoon or flat spatula to ensure it bakes into a cohesive crumb.
- Bake for approximately 42-50 minutes, or until the top is lightly browned and a toothpick inserted into the fruit filling comes out mostly clean. My oven typically bakes these in about 45 minutes.
- Remove the pan from the oven and allow the bars to cool completely on a wire rack while still in the pan. After about an hour, transfer the entire pan to the refrigerator to speed up cooling and firm them up.
- Once completely cooled, use the parchment paper overhang to lift the entire slab of bars out of the pan and place it on a cutting board. Using a sharp knife, cut the bars into squares. Store any leftover bars as instructed in the storage section.
Nutrition
Notes
For the best crumbly texture, always use very cold, cubed butter. If rhubarb is unavailable, use all strawberries, adjusting cornstarch as needed. Quick or steel-cut oats can be substituted, or omitted. Any milk, including non-dairy, works. Avoid overmixing the crumb mixture to prevent a tough crust. Cooling completely is crucial for clean slices; chilling in the fridge helps. Taste fruit filling to adjust sugar if needed. Optionally pre-bake the crust for 10-15 minutes for a firmer base. Don't worry if the crumb mix seems dry initially; it will come together when pressed. Enjoy plain, or serve warm with vanilla ice cream or whipped cream, or with coffee/tea. Store in an airtight container at room temperature for up to 2 days, or refrigerate for up to 1 week. Bring to room temp before serving. Bars freeze well for up to 3 months; thaw overnight in the fridge, then warm to room temperature. Experiment with other berries (blueberries, raspberries), lemon zest, or warm spices like cardamom. Nutrition information is estimated based on common ingredients and serving sizes and may vary.