Chop the onion, carrot, celery and garlic finely. Then melt the butter in a saucepan over medium heat, and add the chopped vegetables. Saute the veggies in butter until soft and lightly browned, about 5 minutes.
2 Tablespoons Unsalted butter, ¼ Onion, ½ Carrot, 1 stalk Celery, 2 cloves Garlic
Sprinkle the flour over the vegetables and stir well, until it comes together as a roux. Continue cooking until the roux is golden brown. Make sure it doesn't get too dark!
2 Tablespoons Flour
Pouring slowly, add the red wine while stirring constantly. Scrape up any browned bits, and let the wine simmer for a few minutes.
1 cup Red wine
Add in the beef stock, then the tomato paste, bay leaf, and thyme. Stir to combine.
2 cups Beef stock, 2 Tablespoons Tomato paste, 2 Bay leaves, 3 sprigs Fresh thyme
Bring to a simmer, then reduce to low heat. Let it simmer gently for approximately 1 hour, stirring occasionally.
After it's cooked, remove the bay leaves and thyme, then pour the sauce through a fine-mesh strainer over a mixing bowl. Press down on the vegetables to extract as much liquid as possible.
Rinse the saucepan, then return the sauce to the pan. Season with salt and pepper to taste, simmer an additional 5 minutes, and serve!
Salt and pepper