Unless you are very lucky and you've bought a fully-trimmed veal pocket from the butcher, trim the veal breast of the excess fat and connective tissue. Keep in mind that you want to make a pocket in there, so as you cut away the gristly parts, be gentle with the lean, meaty parts. Take your time and you'll get it. Season the pocket with salt and pepper.
In a skillet over medium heat, cook the fennel and onions until the fennel is tender. Remove the pan from the heat and add all the other ingredients, stirring to blend completely. Remove from the pan.
Return the pan to the burner and add a tablespoon of olive oil. When it shimmers, put the veal breast in and brown it on each side. Remove from the pan to a cutting board.
When the veal has cooled enough to handle, stuff the stuffing into the pocket, as much as will fit. It's a good think to really pack it in there. Close the pocket to the extent possible with toothpicks or string.
Put the veal pocket on a broiler rack above a pan of water, and into the oven at 350 degrees. Roast until a meat thermometer inserted into the center reads 175 degrees--about an hour and fifteen minutes.
Move the veal pocket to a clean cutting board and allow to rest for ten minutes. Slice and serve.
