banana-oat crumble bars 
from vanillasugarblog.com

crumble:
2 cups all-purpose flour
1 cup rolled oats
½ ts baking powder
½ ts baking soda
couple dashes of cinnamon, optional
1 cup sugar
½ ts salt
1 cup butter, room temp
1 large egg

banana filling:
2 ripe bananas, mashed fairly well
juice of half a lemon
2 TB light brown sugar
1 TB sour cream
1 egg yolk

cook notes: The crumble bars are really tasty when they are crispy. So you might want to bake them to the full 40-45 minute mark.
Look for golden brown (not light golden brown) to know when they are done.
As I stated in the blog post, it might be a good idea to sauté the bananas with a TB of butter and some spiced rum before using. 
I know it would be a great boost in taste. If you do this, then omit the lemon juice step.
If you want bars then let the crumble cool a bit before slicing, if you want warm gooey crumble then serve immediately with vanilla ice cream! 
So good. But remember the filling will be hot!

In a small bowl, mash the bananas, sprinkle with the lemon juice, stir, set aside.
Preheat the oven to 350F. 
Line a 9-inch square baking pan with aluminum foil and lightly grease or if you have nonstick pan then just spray with non-stick spray.

For the crumble: in a large mixing bowl, whisk together all the dry ingredients (and the oats).
Add in the butter and egg, mix until crumbly and just combined.
Take the crumb mixture, divide in half and put one half in the bottom of the pan. Making sure to get all the corners.
Take the mashed bananas, add in the brown sugar, the sour cream, and egg yolk. Mix well.
Next put a nice layer of the banana mixture on top of the crumb dough; try not to go to close to the edges. There might be some banana mixture leftover.
Taking the remaining half of the crumb mixture, and add it to the top of the banana filling.
Please do this by adding it in clumps/balls AND do not press down.
Just make sure to put the mixture on loosely, and evenly; getting the corners covered too.

Bake for 40-45 minutes, until golden browned.
I wanted my crumble fairly crisp, so I went the whole 45 minutes.
It’s really good when it’s nice and crispy.
You need to let bars cool completely in order for them to set up right. OR serve right away if you want traditional warm gooey crumble with vanilla ice cream!

Makes about 12 bars depending on how you slice them.