Raspberry Streusel Bar with Lemon Cream Filling

1 c unsalted butter, softened
3 c flour
1 1/2 c old fashioned oats
1 1/2 c brown sugar
1 t salt
1 t baking powder
1 egg, separated
14 oz can sweetened condensed milk
1/2 c fresh lemon juice
2 t lemon zest
2 1/2 c fresh raspberries
Preheat oven to 350 degrees. Line a 9 x 13 pan with foil, leaving a 1" overhand. Lightly butter foil.
Combine flour, oats, sugar, salt, and baking powder. Cut in butter. Reserve 2 c of crumbs for topping.
Blend egg white into remaining crumbs and press into bottom of the pan. Bake the crust 10-12 minutes.

Meanwhile, whisk together the condensed milk, lemon juice, zest and egg yolk. Let stand for five minutes until thickened.

Sprinkle raspberries evenly over hot crust and then drop spoonfuls of the lemon mixture over the berries. Spread gently with a spatula to distribute a little more evenly. Be careful not to crush the berries. Bake until the lemon mixture begins to form a shiny skin, 1-8 minutes.

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

Let bars cool in the pan for about an hour. Refrigerate until firm. Lift out using the foil overhang and cut into squares.