For the fruit filling:

1. Preheat your oven to 350 degrees. In a medium-sized bowl, toss together the apple slices and blueberries with the sugar, brown sugar, cinnamon and flour until completely coated. Transfer to a 9×9 baking dish or one of similar size.

For the brown butter crisp topping:

1. Brown the butter in a small saucepan over low heat by allowing it to melt and bubble. Watch closely and stir occasionally as the butter will brown quickly once its bubbled down. The desired result is a rich, golden brown color and a toffee-like smell.
2. Pour the brown butter into a small bowl and add in the flour, oats, sugar and vanilla. Stir to combine and from a crisp-like topping.
3. Evenly top the prepared fruit filling with the crisp topping. Place the baking dish on top of a sheet pan lined with parchment in case of bubbling over.
4. Bake for 50-60 minutes, or until the crisp topping is golden brown and the fruit filling is bubbly and cooked through. Serve warm with vanilla ice cream or whipped cream. Enjoy!
5. Serve