Preheat & Prep. To start, preheat oven to 350 degrees F. Grease a 2 quart (8"x8") baking dish with cooking spray, coconut oil, or butter (if not vegan).
Make Chia Egg. In a small bowl, make your chia "egg" by combing 1 Tbsp chia seeds + 3 Tbsp water. Let sit for 2-3 minutes to gel, while you mix up your other ingredients.
Combine Dry Ingredients. In a large bowl, combine oats, baking powder, salt, cinnamon, nutmeg, cardamom, and pecans or raisins. Stir to combine well.
Add Wet Ingredients. Next, add milk, applesauce, chia "egg," diced apples, and vanilla. Stir to combine well.
Bake. Pour mixture into your prepared baking dish. Smooth the surface with a spatula. Bake at 350 degrees F for 25-30 minutes, or until just golden on top.
Serve & Store. Enjoy warm with a drizzle of maple syrup and milk. Store leftovers covered (or in an airtight container) in the fridge 2-3 days. When reheating leftovers, you'll likely want to add a splash of milk.