Preheat your oven to 200°C/400°F (or 180°C/350°F if you're using a fan or convection oven). Have 1 or 2 large baking trays to hand, lining them with baking paper if necessary.

Mix the flax seeds with 1 tablespoon of water and set aside. It will thicken and become gelatinous, and will act as your egg replacement.

In a large bowl, cream the margarine with the caster sugar and brown sugar until fluffy. Add the flax seed mixture to the bowl along with the vanilla extract and mix well.

Add the self-raising flour and mix with a wooden spoon until it starts to stick together. Then use your hands to press it together into a dough. If the dough is too wet, you can add more flour and if it's too dry, add more margarine.

Add the sprinkles to the dough, leaving 1 tablespoon aside, and use your hands to gently knead them in.

Divide the dough into 12 equal-sized pieces. Roll each piece into a ball and flatten slightly, to around 1-inch thick.

Place the pieces of dough onto your baking tray(s), leaving a few inches of space in between each one to allow for spreading.

Use the remaining sprinkles to decorate the tops of the cookies and gently press them in with your fingers.

Bake for 12 minutes. Let them cool completely before you remove them from the tray. They'll be a little wobbly at first but will firm up as they cool.