Make the flax egg by combining 1 tablespoon ground flaxseed with 2½ tablespoon water in a small bowl. Set aside until the mixture becomes gel-like (around 10-15 minutes)
Preheat the oven to 350°F and line a muffin tin with 12 liners.
In a medium bowl, combine flour, salt, baking soda, baking powder, cinnamon, and nutmeg and set aside.
Shred the washed, unpeeled zucchini and measure out one cup, then pat dry with paper towels to remove some of the moisture. Set aside.
Whisk together the oil, milk, and vanilla extract. Whisk in the brown sugar and granulated sugar.
Add in the flax egg, then stir in the shredded zucchini.
Mix in the dry ingredients until combined. Stir in chocolate chips if desired, then fill the muffin tins ¾ of the way full.
Bake 12-15 minutes or until a toothpick inserted in the middle of a muffin comes out clean. Let cool in the tin for 5 minutes then transfer to a wire rack to cool completely.
PLEASE NOTE: I highly recommend using a kitchen scale to weigh your dry ingredients. Metric measurements are found above under the "Metric" tab.FLAX EGG: The flax egg won't work properly in the recipe unless wait for it to become gel-like and goopy. If after 15 minutes it's still watery, you can put it in the fridge for a few minutes to firm it up. The flax seed must be ground up, not whole. You can also use chia seeds to make a chia egg, or a store-bought egg replacer. If you don't follow a vegan diet, you can replace this with one egg.GLUTEN FREE FLOUR: If using gluten free 1-1 baking flour, add 3 tablespoons more milk. MEASURING FLOUR: Properly measure your flour using the scoop and level method or a kitchen scale. SUGAR SUBSTITUTIONS: The sugar can be substituted for coconut sugar at a 1:1 ratio, or maple syrup. If using maple syrup, use around ⅔ cup (or ½ cup if you like the muffins to be less sweet). Depending how wet your zucchini is, you may need to reduce milk by 2 tablespoons, but if the batter seems too thick, add in the 2 tablespoons of milk after.It is important to note that any substitutions to the original recipe will slightly change the texture of the muffins. This includes different sweeteners and flours.OPTIONAL MIX INS: I like to add in ½ cup of chocolate chips to these muffins. You can also add in cranberries or chopped nuts too!TO MAKE INTO ZUCCHINI LOAF: To make these muffins as a loaf, use a 9x5 loaf pan, and bake at 350°F for around 45-55 minutes, or when a toothpick inserted in the middle comes out clean.Storage and Freezing Instructions: Store muffins for 2-3 days at room temperature in an airtight container. Freezing is my favorite way to have fresh muffins on demand! Freeze the cooled muffins in a ziploc freezer bag for up to 2-3 months. When ready to eat, take one out of the freezer and microwave it for 30 seconds (which makes them taste fresh out of the oven), or let it thaw at room temperature.