Blackberry sage sauce

2 cups Zinfandel wine
1 ½ pints blackberries, rinsed and well drained
2 cups brown veal demi-glace, or low-sodium veal or beef stock that has been boiled until reduced by half
2 Tablespoons unsalted butter
salt to taste
juice of ½ lemon, or to taste
2 sprigs fresh sage
Pour the wine into a medium-sized saucepan and bring to a boil. Add the blackberries and cook, stirring occasionally, for about 10 minutes, until the berries are soft. Add the demi-glace and bring to a boil. Lower the heat and cook, stirring occasionally, for about 10 minutes, until the sauce coats the back of a spoon.
Strain the sauce through a sieve and whish in the butter. Season with salt and lemon juice. Place the sage in the sauce and let it steep for 10 to 20 minutes, or until ready to use. Keep warm. Remove sage before serving. Compliments game meat, chicken, beef.