Preheat oven to 160C fan
Generously grease and line a deep, large baking tray, approximately 15 x 10 inches (38.1 x 25.4 cm) in size with parchment paper. The tray should be about 2 inches deep.
In a large bowl, cream the margarine and sugar together using an electric hand mixer until pale and fluffy.
Add in the eggs, one at a time, mixing between each addition, until combined
Add the milk and vanilla extract and mix again.
Combine the flour and baking powder and fold this into the creamed mixture until a smooth batter is formed.
Transfer the batter to the prepared baking tray and spread evenly using the back of a spoon, spatula or palette knife.
Bake for 25-30mins. Once baked set aside to cool.
In the meantime, prepare the fillings. Begin by making the jam filling. Combine all the ingredients except for the chopped strawberries in a small saucepan. Place this over medium-high heat and stir occasionally, breaking the raspberries with a wooden spoon as you do so.
Allow to cook for about 5-8 mins then transfer into a bowl to cool.
Once cooled, stir in the chopped strawberries and transfer them into a piping bag. Set aside for later.
Make the cream by combining all the listed ingredients. Using a balloon whisk, whip to soft peaks and transfer into a piping bag with a nozzle of your choice and set aside.
Using a 6cm round cookie cutter, cut out rounds from the traybake. You should get 16 round pieces of sponge in total (reserve the off cuts of the sponge for another time).
Pipe a border of cream around the edge of 8 of the mini sponges and fill the centre with jam. Sandwich the cakes together with the 8 plain sponges.
Decorate the top of the mini cakes with more cream, jam and a sliced strawberry.