Soak 1 tbsp chia seeds in 2 tbsp cold water for at least 15 mins to allow the chia seeds to absorb the liquid and become sticky and gelatinous. This quantity replaces 1 egg in a cake mixture and the chia seeds will bind the mixture together in place of the egg. It won’t taste the same or be the same texture as it’s not an egg but it will work to bind things together.
Soak 1 tbsp flaxseeds in 2 tbsp cold water for at least 15 mins to allow the flaxseeds to absorb the liquid and then place in the fridge for 15 mins for it to become sticky and gelatinous. Use as you would the chia seed egg but be aware that the flaxseeds may taste and smell a tiny bit fishy due to the high Omega 3 – the same essential fatty acid that is present in oily fish.