How can I make parmesan spreadable?
I would suggest making a Mornay sauce (Béchamel sauce with cheese) which you should find will hold together well and provide an unctuous, rich, spreadable texture.

Simply melt butter in a saucepan over a medium-low heat, whisk in an equal quantity of flour, cook it out a little, then add cold milk, whisking all the while, until you get a smooth sauce like consistency. Then dump in a load of grated parmesan, stir it through, decant to a bowl and cool.