For what it's worth, I've noticed that there's a fine tension between the rice being finished and then developing that creaminess. If one focuses too much on keeping a hint of al dente, then you're likely to pull the dish when the rice is fully cooked but not fully creamy yet. Another minute often finds it starting to "make its own gravy."
I don't know about mascarpone
but of course stirring in a little Parmigiano and butter at the end (a la Marcella Hazan) will also take it up the creamy ladder a bit more. But even a vegan risotto - using any of the varieties - will get deliciously creamy as long as you cook it to that point, in my experience at least.