Peel the skin from the apples and grate on the coarse side of a cheese grater. Set aside. (To prevent browning, place grated apples in a bowl and cover with lemon juice and water. Drain before adding to the batter.)
Preheat oven to 350°F/180°C.
In a large bowl, beat the eggs with a whisk until foamy and pale.
Add the greek yogurt, honey, and vanilla, to the bowl and whisk until the mixture is thick and well combined.
Sprinkle on the rolled oats, baking powder, salt, cinnamon, and the grated apple.
Use a spatula to fold the wet and dry ingredients together.
Pour in the almond milk and continue mixing until everything is well incorporated.
Using a medium ice cream scoop, portion the batter into 12 muffin tin cups lined with cupcake liners.
Top with your choice of toppings.
Bake for 35-40 minutes, until the muffins have set and just started to turn golden brown.