Lemony Blueberry Streusel bars

I found this recipe awhile back on recipegirl.com.  (here's the link to the original recipe, except I don't think I changed anything.  It's just about perfect.) So yum.  I've taken platters of these babies to several church functions, and they always disappear quickly.  I NEVER have leftovers. In fact, sometimes if I am late hitting the dessert table, I won't even get to try one.  (I've learned to keep a small reserve at home)

Lemony Blueberry Streusel Bars

8 ounces (1 cup) butter, softened
3 cups flour
1 1/3 packed light brown sugar
1 1/2 cups old fashioned rolled oats (not quick oats)
1 tsp salt
1 tsp baking powder
1 large egg, separated
14 ounce can sweetened condensed milk
1/2 cup freshly squeezed lemon juice
2 tsp grated lemon zest
2 1/2 cups room temperature blueberries.  (about 13 oz) washed and drained on paper towels.

Preheat oven to 350.  Line 9 x 13 inch metal baking pan with foil leaving a 1 inch overhang on the ends.  Spray foil with cooking spray- bottom and sides of the pan.

In a large bowl, whisk together flour, oats, sugar, salt, and baking powder.  Using a pastry cutter (or your fingers) blend the butter completely into the flour mixture. (I used my food processor, mixing in the oats last, mixing until the oats are just barely combined) Transfer 2 cups of the crumb mixture to another bowl and reserve for the topping.

Blend the egg white into the remaining crumbs, and then press the mixture into the bottom of the pan to form a level crust.  Use the bottom of a flat, wide glass to tap the mixture and even it out.

Bake the crust 10-12 minutes, or until it starts to form a dry top.

Meanwhile, in a medium bowl, whisk condensed milk, lemon juice, and zest, and egg yolk.  Let the mixture stand for 5 minutes.  (It will begin to thicken)

Sprinkle blueberries evenly over hot crust and then drop spoonfuls of the lemon mixture over the blueberries.  Spread gently with a spatula to distribute as evenly as you can.  Bake until lemon mixture begins to form a shiny skin- 7 to 8 minutes.

Sprinkle reserved crumble topping over the lemon-blueberry layer, pressing the streusel between your fingers into small lumps as you sprinkle.  Bake until filling is bubbly at the edges and the topping is brown, 25 to 30 minutes.

Let bars cook in the pan on a rack until just warm, about an hour.  Carefully lift them out of the pan using the foil overhang and transfer to a wire rack to cool completely.  Remove foil and cut into 24 bars when cool.  (If you have time to chill the bars, they're easier to cut cleanly when chilled- plus, I think they taste better chilled.)

Yield:  about 24 bars

Cooking tips- bars may be stored at room temperature for a few hours, but otherwise should be stored in the refrigerator.