1. – In a large Dutch oven or heavy-bottomed pot, heat the olive oil over medium-high heat. Add the short rib pieces and brown on all sides, about 3-4 minutes per side. Remove the short ribs from the pot and set aside.

2. – Add the onion to the pot and cook for 5 minutes, stirring occasionally, until softened. Add the garlic and cook for 1 minute more.

3. – Pour in the red wine and use a wooden spoon to scrape up any browned bits from the bottom of the pot. Bring to a simmer and cook for 2-3 minutes.

4. – Add the crushed tomatoes, thyme, and bay leaf. Return the short ribs to the pot and bring to a boil. Reduce heat to low, cover, and simmer for 20-25 minutes, until the short ribs are very tender.

5. – While the short ribs are simmering, place the potato cubes in a large pot and cover with cold water. Bring to a boil over high heat, then reduce heat and simmer for 15-20 minutes, until the potatoes are very tender.

6. – Drain the potatoes and return them to the pot. Add the milk, Parmesan, and butter. Mash with a potato masher or ricer until smooth and creamy.

7. – Taste the ragu and season with salt and pepper as needed. Serve the short rib ragu over the Parmesan mashed potatoes.