01 -
Let the pan chill out on a wire rack. Give the bars at least a half hour before you try to cut them. They'll slice much cleaner this way.
02 -
Pop it in the oven for 55 minutes or so till the topping looks light golden and the sides are set. If your berries aren't frozen, the bake can go 10 to 15 minutes quicker.
03 -
Dump the berry mixture right over your crust and spread it out. Take the saved crumb and sprinkle it on top, giving the mix a good squeeze in your palm for bigger chunks.
04 -
Gently toss the blueberries in the bowl with sugar, cornstarch, and a splash of lemon juice till everything's coated.
05 -
Keep about a big cup of crumbs aside for the top. Use the rest and press it tightly in your lined pan, making sure it's flat and set.
06 -
Melt your butter in a big microwave-safe bowl. Toss in oats, both sugars, a pinch of salt, and flour. Stir till you get something sandy, with some bigger bits here and there.
07 -
Fire up the oven to 350°F. Line a square 8-inch pan with foil. Spray it with nonstick spray so nothing sticks later.