Add lemon zest and a couple of tablespoons of melted unsalted butter, a few tablespoons of caster sugar (optional), and a few tablespoons of juice from the fruit.
Mix well and press into the base of the dish. Place in the fridge to set.
For the raspberry layer place a punnet or two of raspberries in a saucepan with a tablespoon of lemon juice over a very low heat.
When the raspberries have collapsed and released all their juices add caster sugar to taste (some like it more tart and less sweet) and a some gelatine.
Leave to cool and then spread on to the buscuit base and return to the fridge.
For the mousse hull and chop your strawberries. Place in a pan with a tablespoon of lemmon juice and a dash of water. Put on a low heat until the fruit has collapsed and push through a sieve.
Soften gelatin leaves in water and a little of the strawberry juice for a few mins.
Return to strawberry juices to the pan and add the gelatine and caster sugar to taste. Heat gently until all the sugar and gelatin has disovled. Place in the fridge to cool.
When cooled mix greek yoghurt, creme fraiche and the strawberry mixture together and spread over the top of the rasperry and buscuit mix.
Return to fridge to set.
Decorate with extra fruit.