Preheat the oven to 350°F (175°C).
Line a 12-cup muffin tin with paper liners or grease well.
Whisk the wet ingredients. In a large bowl, whisk eggs, milk, oil or melted butter, honey or maple syrup, and vanilla until smooth.
Combine dry ingredients. In a separate bowl, stir together coconut flour, baking powder, and salt. Break up any lumps with a fork.
Mix gently. Add the dry ingredients to the wet. Stir until just combined.
The batter will thicken as the coconut flour absorbs liquid—let it rest for 2–3 minutes.
Adjust consistency if needed. If the batter seems too thick (like cookie dough), add 1–2 tablespoons of milk. It should be scoopable, not runny.
Fold in add-ins. Stir in chocolate chips, blueberries, or nuts if using.
Fill the muffin cups. Divide batter evenly between cups, filling each about 3/4 full. Smooth the tops with the back of a spoon.
Bake. Bake for 16–20 minutes, or until the tops are golden and a toothpick inserted in the center comes out mostly clean.
Cool. Let muffins cool in the pan for 5 minutes, then transfer to a wire rack to cool completely.
They set up as they cool.