Grilled Portobello with Shallot Butter

Wipe portobello caps clean with a damp cloth. Using the tip of a paring knife, score the top of each cap in a shallow crosshatch pattern — cuts approximately 5 mm deep — to help the marinade penetrate and promote even charring.

Combine softened butter, minced shallots, garlic, white wine, thyme, Dijon mustard, white wine vinegar, fleur de sel, and black pepper in a bowl. Mix thoroughly until fully incorporated into a compound butter.

Brush the gill side of each mushroom generously with the compound butter mixture, then turn and coat the cap side with olive oil. Reserve the remaining compound butter for basting.

Place the mushrooms gill-side down in a single layer on a tray, dollop any remaining compound butter over them, and cover loosely with cling film. Marinate at room temperature for 30 minutes.

Heat a cast-iron grill pan or outdoor grill over high heat until smoking hot — a drop of water should evaporate on contact within 1 second.

Place the mushroom caps gill-side up on the grill. Cook for 6–7 minutes without moving until the cap side develops deep grill marks and releases cleanly from the grate.

Flip the caps so they are gill-side down. Spoon any pooled butter from the tray over the gills. Grill for a further 6–7 minutes until the gills are bubbling, deeply caramelised, and the mushrooms have collapsed slightly in the centre.

Transfer the mushrooms to a warm plate and rest for 2 minutes. Finish with a scatter of freshly chopped flat-leaf parsley and a pinch of extra fleur de sel. Serve immediately alongside grilled or toasted baguette to mop up the shallot butter.