Preheat oven to 350F and spray a 9 inch square dish with some cooking spray.
In a bowl using an electric mixer mix together the apple sauce and ¼ cup of brown sugar, add in the egg and mix well, then add in the peanut butter and vanilla and mix till well blended.
Stir in the flour, oats, baking powder and soda.
Pour batter into the baking dish and spread out evenly.
In a small bowl mix together the crumble ingredinets, flour, brown sugar, peanut butter and butter. I find using a few knives and cutting it (like you would cold butter into flour) works well to form the crumble texture you want.
Sprinkle on top of the batter then bake in the oven for 30 minutes.
Let cool then cut into 12 equal bars.
*Optional to melt and drizzle a little peanut butter on top, I highly recommend this and you can do it over the whole thing or just per bar when you are ready to eat one.
These bars store well in a sealed container and after a day or two I put them in the fridge.
*Note- You could probably substitute with PB2 in wet form although I have not tried so I can't give an honest answer to if they will turn out the same.