Start by mixing the butter and caster sugar together until well combined and creamy looking. This is best done in a stand mixer with the paddle attachment for 3-5 minutes
Add the egg and vanilla extract, and mix until fully incorporated
Add the plain flour and salt, and mix until combined and it starts to clump together
Bring the mixture together into a smooth dough with your hands, and form into a rough disc shape. Wrap the dough in cling film and put it in the fridge to chill for 30 minutes
Meanwhile, pre-heat your oven to 160C Fan/350F/Gas Mark 4, and line a few baking trays with baking paper
Using a rolling pin, roll the dough out onto a floured surface to a thickness of 5mm. Keep turning the dough as you roll, to ensure it doesn't stick to the surface, and add more flour underneath as needed
Cut out your biscuit shapes and place them onto the lined baking trays. You will need to re-roll out the dough to use it all up
Bake the biscuits for 10-12 minutes, until just starting to go slightly golden around the edges. Leave to cool on the trays for at least 10 minutes before moving to cooling racks to cool fully
Roll out your fondant, which you will need to do in batches, onto a surface dusted with icing sugar. Keep the fondant moving and add more icing sugar underneath if needed so it doesn't stick. Cut out the same shapes as your biscuits. Brush some edible glue in a very thin layer on the back of the fondant, or on the top of the biscuit, then place the fondant on top of the biscuit and smooth it out with your finger
Set the biscuits back on the cooling rack for the fondant to firm up. You can add any additional decor at this point
Store in an airtight container in a cool place for 3-4 days (although they can last up to a week), you can also freeze them
Video
Notes
Make sure all your ingredients (particularly the butter and egg) are at room temperature before you start baking.
I prefer to use unsalted butter for this recipe, you can also use a baking spread but you may need to add a little extra flour due to the higher water content in baking spreads.
For the best flavour, make sure to use a good quality vanilla extract and not an essence. You can also use a vanilla bean paste. Or to add some flavour to the biscuits, you could use and orange or lemon extract for example.
Although I provide cup measurements, I highly recommend weighing your ingredients out using digital kitchen scales. It is the most accurate way to measure ingredients and will ensure the best results. Digital scales are very low cost and can be purchased for around £12 ($16.50) .
For teaspoon (tsp) and tablespoon (tbsp) measurements, please use measuring spoons and not the type of spoons you eat with. Again this will ensure accuracy and provide the best results.