Preheat oven to 180° C (350° F), rack in centre position. Place paper liners in 12 muffin cups.
In a bowl, combine the flour, cornstarch, baking powder, chia seeds, cinnamon, and salt. Add the maple syrup and melted coconut oil.
Gradually add the milk substitute, lemon juice and zest, and the vanilla, stirring with a wooden spoon just enough to moisten the mixture without developing gluten. Add the nuts.
Put heaping ice cream scoops of batter into the muffin cups. Bake for 30 minutes.
Remove from oven and allow the muffins to cool slightly before taking them out of the tin.
