3 saffron risotto with marrow Recipes

center-cut beef or veal marrowbones (2 1/2 to 3 lb), beef-veal demi-glace concentrate such as more than gourmet (2 1/2 oz), water, crumbled saffron threads, minced shallot (1 large), unsalted butter, carnaroli or arborio rice, dry white wine, salt, black pepper, grated parmigiano-reggiano (1/2 cup) plus additional for serving, garnish: coarse sea salt (crushed if large)

uncooked arborio rice, unsalted butter, divided, beef stock, beef marrow, onion, thinly sliced, saffron powder, dry white wine, salt to taste, grated parmesan cheese