Prep the apple. Core and dice 1 medium apple into small cubes. No need to peel unless you prefer it; the skin adds fiber and color.
Warm the base. In a small pot, add 1/2 cup rolled oats, 1 cup milk (or water), the diced apple, 1/2–1 teaspoon cinnamon, a pinch of salt, and a splash (about 1/4 teaspoon) of vanilla.
Cook the oats. Bring to a gentle simmer over medium heat, then lower to medium-low.
Stir occasionally for 5–7 minutes, until the oats are creamy and the apples are tender. If it thickens too quickly, add a splash more liquid.
Mix in protein. Remove the pot from heat. Whisk 1 scoop of protein powder with 2–3 tablespoons of cool milk or water in a small cup to make a smooth slurry.
Stir this into the warm oats until fully combined. This helps prevent clumping.
Adjust sweetness and thickness. If needed, add a little sweetener and more warm liquid for a looser texture. Stir in 1 teaspoon chia or ground flax if using.
Serve and top. Spoon into a bowl. Finish with extra apple, a few nuts, a sprinkle of cinnamon, or a drizzle of almond butter for richness.