Before you start this recipe, Sterilize your jars by filling with boiling water and allow to dry in a warm oven. To make the lemon curd, lightly whisk the eggs in a medium-sized saucepan, then add the rest of the ingredients and place the saucepan over a medium heat. Now whisk continuously using a balloon whisk until the mixture thickens, about 7-8 minutes. Next, lower the heat to its minimum setting and let the curd gently simmer for a further minute, continuing to whisk. Immediately remove it from the heat and pour the lemon curd into the hot, sterilized jars, filling them as full as possible. Cover straightaway with waxed discs and seal while it is still hot. The lemon curd will keep for several weeks, but it must be stored in a cool place. For this recipe you only need 3 tbsp of lemon curd. Meanwhile, prepare the stewed berries by placing them into a pan with the sugar and their juices and cook for 10-15 minutes to cook down and reduce. Allow to cool down completely. When you are ready to put the recipe together, crumble the vanilla sponge into 4 Martini glasses. Soak with the juice from the stewed berries. Place the yogurt and lemon curd into a bowl and mix together. Add in the stewed berries, and lightly mix together, but not completely so that there are streaks. Spoon into the glasses on top of the sponge and chill for an hour. Serve decorated with extra berries on top.