1. Cook onions low and slow in olive oil + butter until deep golden and jammy (about 25–30 minutes), stirring occasionally.

2. Season with thyme, a pinch of salt, and black pepper.

3. In the same pan, brown the sausage until cooked through (about 8–10 minutes). Drain excess grease if needed.

4. Add onions back in, pour in beef broth, and simmer 3–5 minutes until most liquid is gone. Let filling cool 10 minutes.

5. Preheat oven to 400°F (200°C). Line a baking sheet with parchment paper.

6. Roll puff pastry on a lightly floured surface into a rectangle. Spread filling in an even strip, leaving a 1-inch border.

7. Sprinkle Gruyère over the filling. Roll tightly into a log and seal the seam with a little egg wash.

8. Slice into 12 equal rolls and place cut-side up on the baking sheet.

9. Brush tops with egg wash. Bake 30–35 minutes until puffed and deeply golden.

10. Cool 5–10 minutes before serving (filling is hot!).