If you want to make a large batch of these muffins to reheat, cool the muffins completely then wrap individually with cling film, and keep in a tightly covered container in the fridge. To reheat, unwrap, place in a small bowl, cover with a small plate or saucer, and microwave on HIGH for 30 seconds.
In a large mixing bowl, whisk together the two flours, baking powder, salt, baking soda and sugar.
Throw in the cubed cheeses and toss to coat each piece with flour.
In another mixing bowl, lightly beat the eggs and milk.
Take cooled spinach mixture and stir into the flour mixture. Make sure to scrape all the butter from the pan and into the flour.
Pour the milk-egg mixture into the flour mixture and mix just until the dry ingredients are moistened, about 12 turns. Overmixing muffin batter results in tough muffins.
Using an ice cream scoop, fill the muffin holes with the batter, about 3/4 full.
Bake at 350F for 25 to 30 minutes or until a skewer inserted at the center of the muffin comes out clean.
Cool the muffins in the pan for five minutes. Transfer to a rack.
These muffins are best served while warm and the cheeses are still soft.