So I tackle it a different way and make it in a slice tin. Just as yummy but four times as fast to do.
I use the Edmonds recipe but double it. This will then make a slice in a sponge roll tin. (this has already been doubled)
First cream the butter and sugar well, then add the eggs one at a time. Sift the dry ingredients into this and mix until the crumbs are sticking together and looking chunky - like this
Press just over half the mixture into a baking paper lined tray (I use an old fashioned sponge roll tin)
Soften the jam in the microwave with a good squirt of lemon juice. This should make it runny enough to just pour on and have it easy to move around the slice. If you don't do that the jam is very hard to spread on the biscuit base. Traditionally the jam is raspberry jam - but we ran out of the homemade stuff months ago. What I do still have in the cupboard is blackcurrant jam and that makes a gorgeous tasting slice. Use what jam you like. Pour the rest of the biscuit crumble onto the jam.
Smooth out the crumble and press gently. You want it setting together but not so hard that the jam oozes up through this layer. Bake at 180C for approx 20-25 minutes. Until slightly golden and looking cooked all over.
It is important to add a runny icing as soon as you take it out of the oven. I then sprinkle a packet of jelly crystals on top - just because this is how I have always made it. But you could do hundreds and thousands. Or nothing at all. Once cooled but not cold, cut into slices.Belgium slice
1/2 c brown sugar
4 C plain flour
2tsp baking powder
2tsp ground ginger
2tsp mixed spice
3/4 cup of jam and a squeeze of lemon juice.
Pink icing made how you like to make icing.
Packet of blackberry jelly (optional)
I link to these places.