More detailed directions (with pictures)
Separate the egg whites from the yolk.
Mix the flour, baking powder, and baking soda by passing them through a sieve couple of times.
Dissolve the coconut sugar and stevia in milk.
Add vanilla extract to milk.
Mix the milk mix with the flour.
Add melted butter to the mix.
Add egg yolk to the mix.
Mix the ingredients well with a hand mixer. The mix will be little dry initially, but it will reach the correct consistency once we mix egg whites.
Take the egg whites in the bowl and use a whisk/mixer to get stiff peaks. You may use a hand mixer to beat the eggs. it takes around 15-20 seconds with a mixer or 2-3 minutes with a whisk.
Add these to the muffin mix.
Use spatula to mix the egg whites with the muffin mix, else use a mixer.
Finely chop the apples, discard the seeds.
Add the chopped apples to the muffin mix.
Pour the muffin mix in buttered and floured muffin pans. Place in the pre-heated oven and bake for 30 to 35 minutes or until toothpick comes out.
Alternatively you may use a water bath to bake the muffins, it will take around 40-45 minutes or until toothpick comes.
The water bath adds moisture to the oven and provides a more even, slower heat source than the direct heat of an oven
Allow the muffins to cool on the rack for 30 minutes.