Heat oil in a large pot over medium heat. Add venison pieces and cook until browned on all sides. This step locks in flavor. Do not overcrowd the pan. Remove meat and set aside.

In the same pot, add onion, carrots and celery. Cook until soft and slightly golden. Stir often to prevent burning. Add garlic and cook for one minute. The base should smell rich and comforting.

Sprinkle flour over the vegetables. Stir well to coat everything evenly. This helps thicken the sauce later. Cook for one to two minutes to remove raw flour taste.

Slowly add red wine while stirring. Then pour in stock and add tomato paste. Mix until smooth. The sauce should look slightly thick and glossy. This creates a rich base.

Return venison to the pot. Add thyme and bay leaves. Season with salt and pepper. Stir gently so everything combines well. Bring to a gentle simmer.

Cover the pot and place it in a preheated oven at 170°C. Cook for about 1 hour 45 minutes. Stir once or twice. The meat will become tender and soft.

Add mushrooms in the last 20 minutes of cooking. Let them soften and absorb flavor. Remove bay leaves before serving. Garnish with fresh parsley and serve hot.