Melt the honey and marmite in a pan over medium heat, then slowly add the sugar and leave for a few minutes to melt and lightly caramelise.
Heat the cream in another pan to just about boiling.
When the sugar has reached a golden caramel colour, add the cream, standing well back in case of spitting. Stir vigourously and continue to cook for a few minutes until the caramel is thick and golden but still liquid. Remove from the heat and leave to cool.
Melt the butter and chocolate in a large pan over low heat.Remove from the heat, add the sugar and stir. Beat in the eggs one by one, then sift in the dry ingredients.
Stir until just combined, then spoon half the mixture into a 20 cm square mould (line as appropriate).
Spoon the cooled caramel over the top, then dollop over the rest of the brownie mixture. Drag a skewer through the mixture to swirl it together slightly.
Bake at 180℃ (350℉, Gas 4) for 25 minutes until well risen with only a slight wobble to it.
Leave to cool, then cut into 12 pieces.
Notes
Please note: calories and other nutritional information are per serving. They're approximate and will depend on exact ingredients used.