I have mixed sour cream with Marmite to make it spread more evenly over banana, and the taste is… not good. The salt overpowers all other components. It’s even worse than plain Marmite banana, because you can actually taste the banana before Marmite diffuses over your tongue. The best combination was cream banana without Marmite, to no surprise.
Marmite cream oat cookie is a surprising discovery. The overpowering saltness of Marmite is balanced by the overpowering sweetness of the oat cookie, the same way salted caramel works. I don’t think the cream is even necessary, you can rub Marmite on the cookie’s hard surface much easier than on the soft banana.
If you like Marmite, you’d probably dig Nutritional Yeast without the extra additives to make something similarly tasting.