Never heard of "marrowfat peas" before. Seems that the german translation is "Kapuzinererbsen", which are also known as "grey peas". But these are brown or grey in colour, and look more like chickpeas, while marrowfat peas look (most of the time, so it seems, per google search) more like green peas, color-wise. Wonder what the difference is.
Mattar Paneer... hmm... great dish

Aloo Mattar is quite popular and very tasty, too!