Biscuit dough: Measure the butter and place it into a small saucepan or in the microwave to melt.
To make the crushed pistachios, simply place the required amount in a small bag or between two pieces of paper and use a heavy object or rolling pin to crush the nuts. They do not have to be super fine.
In a large bowl, mix 45g of the crushed pistachios, flour, sugar, salt, baking powder and vanilla.(The remaining crushed pistachios will be used to decorate.) Add the milk and butter to the dry ingredients and bring them together to form a dough.
Preheat your oven to 160°C fan / 350°F / Gas 4.
Chill the dough in the fridge for 15-30 minutes to make the dough easier to roll out. Roll out between two pieces of parchment paper to a thickness of about 4mm (1/4 inch).
Use a round 5cm (2inch) cookie cutter to cut out the biscuits and arrange them on a lined baking tray. They do not spread so I managed to fit them on one tray.
Baking: Place the tray on the middle shelf and bake for 15-20 minutes. Avoid under baking as this will leave the biscuits soft in the middle. Once baked, leave to cool completely. Jam: Place 100g of fresh raspberries and 50g of white sugar into a small saucepan. Gently simmer the mixture until it has reduced and thickened, approx. 10-15 minutes. Start over low heat and stir often so the sugar doesn’t burn. (You can add a splash of water to help get it started if you would like.)
I add a little cornflour to the jam to ensure it doesn't run out between the biscuits. If you decide to buy jam instead of making it, then as long as it is quite thick you don't need to worry about the cornflour.If you are going to use the cornflour, mix it with a little cold water to form a thin paste and pour it into the jam, stir continuously to avoid lumps forming.Remove from the heat after about a minute.Then using a sift or fine mesh strainer push the raspberry mixture through to remove as many of the seeds as you would like. Use a silicone spatula or the back of a spoon to press the sauce through the strainer.Set aside to cool completely. This can also be done a couple of days in advance and kept in the fridge until ready to use. Assembly: Once the biscuits and jam have completely cooled, dollop a teaspoon of jam onto one of the biscuits and press another one onto it. *See notes.
Chocolate: Melt 2/3 of the chocolate in a small bowl over a pan of boiling water or in the microwave for 30 seconds at a time and stirring until melted.Once fully melted, add the remaining chocolate and stir until completely dissolved.Dip the sandwiched biscuits into the chocolate and place them on a wire rack, sprinkle each biscuit with some of the remaining crushed pistachios and leave to cool.