📖 Instructions

1. Preheat your oven to 375°F (190°C). Line a 9x13 inch baking pan with parchment paper, leaving an overhang on the sides. This makes it easier to lift the bars out later. I often forget this step, and it's *always* a pain to get them out cleanly without the overhang. Don't be like me!
2. In a large mixing bowl, whisk together the flour, powdered sugar, and salt. This ensures everything is evenly distributed. Ever had a bite that was *all* salt? Yeah, avoid that.
3. Add the cold, cubed butter to the flour mixture. Using a pastry cutter or your fingertips, cut the butter into the flour until the mixture resembles coarse crumbs. Alternatively, you can use a food processor for this step, pulsing until the mixture comes together. Be careful not to over-process; you want those buttery pockets for a tender crust.
4. Press the mixture evenly into the prepared baking pan. Use the bottom of a measuring cup to firmly pack it down. Prick the crust all over with a fork to prevent it from puffing up during baking. I like to make a little design, just for funsies.
5. Bake the crust for 15-20 minutes, or until it's lightly golden brown. Keep a close eye on it, as oven times can vary. You don't want it to burn! Remove from the oven and let it cool slightly while you prepare the filling.
6. While the crust is baking, prepare the filling. In a large bowl, gently toss together the sliced rhubarb, chopped strawberries, sugar, and cornstarch. Make sure the fruit is evenly coated with the sugar and cornstarch mixture. Cornstarch is key for thickening the filling and preventing a soggy mess.
7. Once the crust has cooled slightly, evenly spread the rhubarb and strawberry mixture over the top. Be gentle so you don't break the crust.
8. In a separate bowl, prepare the crumble topping. Combine the flour, brown sugar, and rolled oats. Add the melted butter and mix until the mixture forms clumps. You can use your hands for this, but be warned, it can get messy!
9. Sprinkle the crumble topping evenly over the fruit filling. Try to cover as much of the fruit as possible for a nice, even topping.
10. Bake the bars for 30-35 minutes, or until the topping is golden brown and the filling is bubbly. Again, keep an eye on it, as oven times can be fickle. I swear my oven has a mind of its own sometimes.
11. Remove the bars from the oven and let them cool completely in the pan before cutting into squares. This is crucial, as the filling needs time to set. I know it's tempting to dig in right away, but trust me, patience is a virtue here. Use the parchment paper overhang to lift the bars out of the pan, then cut them into squares. Dust with powdered sugar, if desired. And finally... enjoy every delicious bite!