The metric equivalents are probably within 10g/10ml of correct...
1/2 cup (120g) butter
1 1/2 cups (320g) light brown soft sugar
2 egg yolks, well beaten
2 cups (300g) plain flour
2 tsp baking powder
1 tsp ground cinnamon
1/4 tsp ground nutmeg
1/4 tsp ground cloves
1/3 cup (90ml) evaporated milk
1/3 cup strong coffee (I used 60ml pure maple syrup)
1 tsp vanilla extract
2 egg whites, beaten stiff
Cream butter, add sugar and egg yolks and beat again. Mix flour, baking powder and spices in a separate bowl. Add the dry ingredients alternately with the milk, and beat until smooth. Add the vanilla and maple syrup, mix and then fold in the egg whites. Pour into the greased ring tin (this would work in a normal cake tin I'm sure, probably a 20cm diameter one would give a nicer height) then bake at 190c for 25-30 minutes. (I found that the cake was jelly-like at this point, so gave it an extra 5 minutes and the skewer came out clean).
Allow the cake to cool (probably about 2 hours or so) then prepare the frosting/icing...
1 cup (270ml) evaporated milk
1 1/4 cups (300g) white sugar
3/4 cup (150g) light soft brown sugar
2 tbsp butter
1/2 tsp vanilla extract
Blend the milk and sugars in a large saucepan on a medium heat, add butter. Bring to the boil and cook for a few minutes until the sauce thickens, so that a dribble dropped into a glass of cold water forms a soft ball (soft ball stage). Cool for around 20 minutes, then add the vanilla and beat for a few minutes until the sauce thickens enough to spread onto the cake. It thickens slightly more on standing, so spread it as soon as it's done.