Boil down blood orange until almost half remains, add cream and bring to a boil again. Stir in 1 tablespoon cold butter, sugar and beaten eggs. Preheat oven to 120°C (approximately 250°F.)
Pour orange cream in two small, heat-resistant glass jars, close jars tightly and hot water and cook for about 40 minutes in oven.
Cut biscuit into cubes and caramelize with powdered sugar in the remaining butter while stirring for 1 to 2 minutes. Sprinkle again with powdered sugar. Drain crusty sponge cake on paper towels and let cool.
For best results, only open warm pudding when ready to serve, top with sponge cake and dust with powdered sugar.