Preheat the oven to 375 degrees. Roast the hazelnuts until they smell toasty. Remove from oven and let cool for a few minutes. Rub off the skins and cool the nuts another 15 minutes.
In a food processor grind the nuts with the sugar until finely ground but not pasty. With your hands work in the butter, flour and chocolate together. Add the eggs, one at a time. You just need the egg to hold the dough together; you may need only 1.
Butter a 13 1/2 x 5 x 2 1/2 inch deep meatloaf pan. Spread about 2/3 of dough in the bottom and up the sides of the pan, spread the jam in the middle and top with more dough. Bake at 375 degrees for 10 minutes, reduce heat to 350 degrees and bake 5 minutes more, then reduce heat to 300 and bake for 1 hour longer or 1 1/4 hours in all. To test insert a cake tester in dough and it should come out dry. Can be made days ahead of time.