Preheat oven to 350F/ 175C.
In a mixing bowl, combine oats, flour, sugar, cornstarch, baking powder, cinnamon, and salt.
Add the apple, the banana, the dates, and the hazelnuts to the mixing bowl.
Mix olive oil and almond milk in a measuring cup, then pour into the mixing bowl with the dry ingredients. Stir until well combined.
Drop 12 heaping tablespoon-sized mounds onto a parchment-lined cookie sheet. If you prefer smaller cookies, you can level off your tablespoons of dough and make about 15 cookies.
Bake for 15-16 minutes or until the edges of the cookies are slightly browned. (If you're making 15 smaller cookies, bake them slightly less).
Allow your cookies to cool for 5 minutes before removing them from the baking tray.