Preheat the oven to 200C. In a large mixing bowl, add the sugar and orange zest. Using your hands, rub the zest into the sugar for a minute to release the oils from the orange peel.
Add the chia eggs and whisk well until well combined. Then whisk in the orange juice, oil, yogurt, milk, melted butter and vanilla extract, and stir well until evenly mixed.
Stir in the baking powder, baking soda, and salt until well combined.
Fold in the flour and poppy seeds, using a spatula, to form a batter. Ensure not to overmix!
Rest the batter for 10 minutes. Line a dozen muffin tin with parchment liners.
Spoon the batter into the muffin tin, filling each about 3/4 of the way full. Bake 5 minutes at 200C without opening the oven, then reduce the heat to 180C and bake for another 15-20 minutes until golden and a skewer comes out clean.
Remove from the oven and allow the muffins to cool for a minimum of 15 minutes before serving.