Cook the canelones pasta (or similar pasta) according to the package.
In a large pan, cook all the ingredients EXCEPT for the veal, and set the heat to low. Stir occasionally, the mixture has to be juicy, otherwise add a little bit of water. The mixture should be on low heat for about 35 to 45 minutes.
If you are using the veal brain, boil it for about 10 minutes. Remove from the pot.
After cooking the mixture for 35 to 45 minutes, you can add the veal brain into the pan.
Place the mixture into the food processor and blend it to a fine consistency. If you don’t have a food processor, use a blender or another substitute.
Stuff the mixture in the middle of the canelone dough.
Roll up all of the canelones. Pour a little bit of the sauce on the bottom of the baking dish and then add the canelones in a line (or two lines depending on the size of your baking sheet.) Add only one layer.
The canelones can be touching one another,but make sure they are not overlapping. Add some of the white sauce, the grated cheese, and small pats of butter on top (butter is optional).
Bake for about 10 minutes at 350 F, and then broil it for 2 minutes to brown the cheese.