1. Flour -
I like using wholewheat flour for these, but it works perfectly with plain / all purpose white flour as well. The muffins will be a bit paler and they are even softer. (They are soft with the wholewheat too, it's just they are even softer with white flour).
Chop the apple up into small pieces, otherwise it has a tendency to make the muffin seem too crumbly, noting that this muffin batter only uses 1 egg (which is a reason why it's so moist but also means the crumb is not as tightly bound as muffin mixes that use 2 eggs, so you need to ensure the apple pieces are chopped fairly small).
3. MUFFIN TIN SIZES:
There are mini, standard and jumbo muffin tins. This recipe is for standard muffin tins. Standard muffin tin sizes do differ slightly here in Australia - there are 1/3 and 1/2 cup muffin tins. You should get 12 out of this recipe either way because with the 1/3 cup, the batter mounds slightly over the top of the muffin tin hole plus there is a bit left over. With the 1/2 cup, it fills 12 holes pretty much to the top, scraping every bit of batter out of the bowl.
: Don't use this recipe for a cake or loaf, the crumb is too delicate. Use this recipe (YES it is moist too!) -> https://www.recipetineats.com/easy-apple-cake-recipe/
These keep so great in an airtight container for 4 to 5 days, they stay really nice and moist but it's it's really hot and/or humid where you are, keep them in the fridge.
The crunchy top does soften overnight, as it does with anything with a sugar topping. These are also terrific FROZEN - then just defrost before consuming, and yes they are moist even without reheating. :)
If it's super humid and hot where you are (eg Sydney in summer!) these are prone to becoming mouldy because they are so moist!
So store them in the fridge.
6. Recipe adapted
from these Brown Sugar Muffins
by Taste and Tell.
7. Different measures in different countries - read more here
. This recipe is fine to use as written irrespective of what country you are in - except Japan, use weights and ml, not Japanese measuring cups.
assuming 12 muffins.