A very gentle way to make into solid form is to pour milk on a Petri dish as a thin film (3-5 mm thick) and place in a fumehood overnight. Next day, it will be easy to mortar & pestle into a powder. To create a paste from it, add water back but at 1/5 the original amount.
Human milk is much lower in protein (~1%) overall than cow's milk (3.3-3.5%) and additionally the ratio of caseins-to-whey proteins is much lower in human milk (1:2) than cow's milk (3:1). Caseins are the proteins that precipitate to form curds by acid (ie yogurt and some soft cheeses) or by enzymatic hydrolysis of kappa casein with rennet/chymosin (ie most cheeses), while whey proteins are acid stable but can be precipitated with high heat treatment to denature proteins and form intermolecular cystine disulfide linkages (ie Ricotta cheese).
Although the total solids of human milk and cow's milk is similar, most human milk is lactose necessary for brain development. While in cows, due to their massive newborn calf size, require a huge amount of calcium (see ash content of cows milk 0.7% compared to human milk 0.2%), which the primary purpose of casein is to deliver calcium in quantities that would be insoluble without binding to casein proteins as calcium phosphate nanoclusters, with caseins being a protein source for the neonate calf secondary. Typically as the size of the newborn increase, so does the casein content in the milk to support this bone development. In humans, this is also one of the main theories as to why traditionally some geographical regions produce on average taller larger people (Scandinavia - high milk consumption during formative years) vs. shorter smaller people (Far East & Africa - low milk consumption during formative years) -- although this is changing dramatically as the world's access to milk products is not as limited as in past.