Preheat the oven to 190°C, fan 170°C, gas 5. Process the cashew nuts and the xanthan gum in a liquidiser until it forms a fine powder.
Add the dates and water, and continue to process until a smooth paste is formed.
Lightly grease a 4-hole muffin tin. With wet hands, divide the mixture into 4 balls and place one in each hole.
With your finger wrapped in cling film, press the mixture into the base and up the sides. Bake in the oven for 5-6 minutes until firm. Leave in the tin to set, and then carefully move onto a cooling rack.
To make the filling, place the stem ginger, avocado and lime zest into a bowl and whizz with an electric mixer until smooth. Add lime juice to loosen the mixture but keep it firm. Pipe the mixture into each tartlet.
Keep refrigerated until required.
Top tip: you can use this recipe to make 12 mini-size tartlets, perfect as canapés for a party.