Peel and chop the garlic and onion. Sauté with olive oil in a saucepan. Do not brown them.
Pour half of the red wine, vinegar and all of the stock into the pan. Season with thyme and pepper.
Bring the stock to the boil over a high heat. Whisk until half of the liquid is left. Strain the liquid back to saucepan.
Add the remaining red wine and sugar to the sauce and simmer till the sauce starts to thicken. Taste and add salt and sugar if necessary. The red wine sauce should be a little 'over-flavored' at this stage. Butter will smooth the taste.
Add butter a tablespoon at a time to smooth the Red Wine Sauce. Whisk it good. Butter will give the richness and nice sheer for the sauce.