2) With the mixer on low speed, first add the eggs, then the flour, salt, and remaining 60g of butter. Raise the speed to medium-high and beat for 5 mins. Scrape down the bowl and beat to form the dough into a ball. It will be very soft. Cover the bowl with a damp towel and allow it to rise until doubled in size, about 1 hour.
3) Drain the currants, fold them into the dough with a spatula, and spoon into the prepared pan. Smooth the top, cover the pan with a damp towel, and allow to rise until the dough reaches the top of the pan, 50 mins to 1 hour.
4) Meanwhile, preheat the oven to 190°C/gas mark 5 and make the rum syrup.
5) Bake the cake for about 30 mins, or until a toothpick comes out clean. Allow to cool for 10 mins, then tap it out of the cake pan onto a baking rack set over a sheet pan. Pour all of the rum syrup very slowly onto the warm cake, allowing it all to soak in thoroughly. Amazingly, the liquid will be absorbed into the cake, so be sure to use all of the syrup.
5) Heat the preserves with 15ml of water until runny, press it through a sieve, and brush it on the cake. Serve with whipped cream piped into the middle of the cake plus an extra bowl on the side.
6) To make the rum syrup: Place the sugar and 375ml water in a small saucepan and cook over high heat until the sugar dissolves. Pour into a 1L heat-proof measuring cup and allow to cool. Add the rum and vanilla and set aside.
7) To make the whipped cream: Whip the cream in the bowl of an electric mixer fitted with the whisk attachment. When it starts to thicken, add the sugar and vanilla and continue to whip until the cream forms stiff peaks. Don't overbeat, or you'll end up with butter.