Demi-glace is one of those ingredients that I wish I had on hand more often in my kitchen. Made from reducing a long-simmered stock, this beautiful and rich brown sauce is considered a staple in classic cooking, enriching countless sauces and adding complex flavor to soups and stews. This time of year, I love using it to boost the flavors in my special occasion dishes, but I find it a bit too labor-intensive to prepare, so I buy it. My favorite is the duck and veal demi-glace from D’Artagnan. Made using all natural ingredients—loads of aromatic vegetables, water, and wine—D’Artagnan’s secret is to slowly cook it for 48 hours, resulting in a demi-glace that has a rich and deep flavor, adding silkiness and body to my sauces. I keep some in the freezer so I can pull it out whenever I need it.