Make the syrup. Tip 30g of the caster sugar into a small pan and add 2 tablespoons of cold water. Place over low heat and stir until the sugar dissolves. Increase the heat and cook for 3–5 minutes, until you have a golden, caramel syrup.
Meanwhile, prepare the filling. Cut the top and base off the pineapple and carefully cut away the skin from top to bottom. Cut 6 horizontal slices, each about 1cm thick, from the pineapple. Using the 6cm cutter, cut the pineapple slices into neat rounds (eat the trimmings). Using the 1.5cm cutter, cut a hole in the center of each round to remove the core and make 6 pineapple rings.
Divide the syrup equally between the pudding molds. Place a pineapple ring in each mold and a maraschino cherry in the center of each pineapple ring. Set aside.
Heat the oven to 320ºF
Make the sponge. Beat the butter and sugar in a stand mixer fitted with the beater, on medium speed for 3–5 minutes, until pale and creamy, scraping down the sides of the bowl from time to time.
Add the eggs, one at a time, beating well between each addition. With the mixer on low speed, mix in the flour until just combined.
Evenly distribute batter.
Bake for 20-25 minutes, till skewer, comes out clean.
To decorate, whip the double cream to soft peaks and spoon into the piping bag fitted with a medium closed star nozzle. Pipe a rosette of cream on the top of each pineapple cake and finish with a maraschino cherry with a stem.