Finely chop the mushrooms until they resemble coarse mince.
Heat the olive oil in a wide pan over medium–high heat. Add the mushrooms and cook, stirring occasionally, until they release their moisture, dry out and begin to brown.
Add the onion with a pinch of salt and cook for 5–7 minutes, stirring regularly, until softened and lightly golden.
Add the garlic and cook for 30–60 seconds, just until fragrant.
Stir in the tomato paste and cook for 2–3 minutes until darkened and brick-red.
Deglaze with the red wine, scraping up any caramelised bits, and let it reduce completely.
Add the crushed tomatoes and bay leaf. Pour a small amount of water into the empty tomato can, swirl to loosen any remaining tomato, then add it to the pan. Bring to a gentle simmer.
Reduce the heat and cook uncovered for 30–40 minutes, stirring occasionally, until thick and cohesive.
Stir in the milk and simmer for a further 5 minutes. Season well with salt and pepper.