Well "Marmite" is generally regarded as an off-flavour, as it implies autolysis. So just take a normal beer, stress the hell out of your yeast and then just leave it for a few months...
I love Marmite but I'm not sure I'd want it in my beer. If I did, I'd want something that could stand up to such a strong taste, go somewhere in the Old Peculier direction or even bigger.
Given that autolysis can be a characteristic of old beer, the bigger end of Old Ales would probably suit quite well.
And if you partigyle, at least you end up with a few gallons of a drinkable smaller beer....