To make mantha first you needed sattu which was parched or roasted barley or rice flour. The grain was roughly ground and then cooked. Sattu was commonly taken by people when they went on a journey; it enabled a filling meal to be prepared with only a little cooking (Ja.III,343; Vin.IV,80). Sattu was mixed with water or sometimes milk and then boiled, proberly with a pinch of salt, and this produced a thick gruel or porridge. Manthu could be eaten together with something else; in the case of the Buddha, with madhupindika. Madhu means honey or more broadly, ‘sweet;’ pinda means a ball or a lump. So madhupindika could refer to a lump of honeycomb but this seems unlikely in this case given that this food would be awkward to carry. I think it is much more likely that madhupindika was the same