In a small mixing bowl, dissolve yeast in warm milk. Let stand until creamy, about 10 minutes.
Prepare a sweet dough by creaming 50g sugar with the margarine and 1/4 teaspoon salt. Add 1 egg and beat with electric mixer 1 minute until well blended. Add 310g flour, the yeast mixture and 1 tablespoon vanilla. Mix 3 minutes with dough hook or with hands. Turn dough out on floured board and knead for 1 minute. Place in a lightly greased bowl, cover with a towel and set in a warm place to rise for 1 hour.
While dough is rising, prepare the butter filling. In a large bowl, combine 500g sugar, 225g butter and 1/8 teaspoon salt. Add 1 egg and golden syrup. Mix enough to incorporate. Add 280g flour, 4 tablespoons water and 1 teaspoon vanilla. Mix together well and set aside.
Divide dough into two pieces. Place each into a greased 23cm round cake tin. Crimp edges halfway up sides of tins to keep the butter filling from running out underneath. After dough is spread out, punch holes in dough with fork to keep it from bubbling when baking.
Divide butter topping into two equal parts. Spread over dough in each tin. Let cake stand for 20 minutes.
Preheat oven to 190 C / Gas 5. Bake cakes in preheated oven 30 minutes. Do not overbake; the filling should stay gooey. After cakes are cool, sprinkle with icing sugar.
If you can get your hands on fresh yeast, use 20g of this instead of dried active baking yeast.
I didn't have much success with this recipe. The dough didn't rise but I think that's because the milk was too warm. I'm told it tasted nice but it was really heavy and I would've expected the filling to set more than it did. It looked like a messy slop on the plate. I will try it again with cooler milk and will review it again soon - 29 Dec 2014