Melt butter, chocolate and sugars in a large saucepan over a very gentle heat, then remove from the heat.
Grate in the zest of the orange, then squeeze in the juice. Stir until everything is combined.
Beat in the eggs, one by one.
Mix the bicarbonate of soda into the flour and sift a third in. Fold in, then stir in a third of the hot water. Repeat until everything is just mixed.
Pour into a silicone mould, lined tin or a buttered / oiled Pressure-Cook Pro bowl.
Bake for 55 minutes at 180℃ (350℉, Gas 4) in the middle of a preheated oven or until the top is firm and an inserted skewer comes out almost clean. A slight underbake is much better than over baking with this cake.
If using the Pressure-Cook Pro, select the cake function and adjust the time setting to 1 hr.
Leave to cool, then turn out onto a serving plate.
Orange Chocolate Glaze
Squeeze the juice of an orange into a small pan. Add the honey and chocolate and melt everything over a gentle heat. Alternatively place in a bowl over some hot water.
Add the butter, half at a time, stirring until melted.
Pour over the cake, allowing it to dribble down the sides.
Other oranges can be used, but the flavour and sweetness of the cake will vary.
Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.