1. Heat olive oil in a large skillet over medium heat and add the sausages. Cook until browned and fully cooked through, turning occasionally. Remove and set aside.

2. In the same skillet, add more olive oil if needed and toss in the sliced onions. Cook on medium-low heat, stirring often, until caramelized and golden, about 20 minutes.

3. Sprinkle flour over the onions and stir well. Cook for 1 minute to remove the raw flour taste, then slowly add beef stock while stirring to form a smooth gravy.

4. Add salt, pepper, and thyme to the gravy. Let simmer for 5 to 10 minutes until thickened.

5. While the gravy simmers, boil the peeled, cubed potatoes in salted water until tender. Drain well.

6. Mash the potatoes with butter and heavy cream until smooth and creamy. Season with salt and pepper to taste.

7. Plate a mound of mashed potatoes, top with sausages, and ladle onion gravy over the top. Garnish with thyme if desired.