Put the potatoes in a large saucepan, cover with cold water and add a generous pinch of salt. Bring to the boil and simmer for 14 to 16 minutes, until tender. Drain well and leave them to steam dry for 5 minutes.

Heat the oven to 220°C fan, or 240°C conventional. Put a roasting tray in the oven for a few minutes so it gets hot.

In a bowl, mix the crumbled blue cheese, sour cream, Dijon mustard, garlic, lemon juice, half the celery salt and a few grinds of black pepper. Stir until roughly combined. It doesn’t need to be perfectly smooth.

Carefully remove the hot tray from the oven. Add the olive oil and butter. Once the butter melts, tip in the potatoes and turn them to coat. Roast for 20 minutes, turning once halfway through, until the surfaces begin to colour.

Use the back of a spoon or a masher to gently press some of the potatoes so they split open. You’re not making smashed potatoes, just creating more surface area for the topping.

Spoon the blue cheese mixture over the potatoes in small dollops. Return the tray to the oven for 8 to 10 minutes, until the cheese softens and the potatoes are golden at the edges.

Scatter over the chives, the remaining celery salt and the parsley if using. Taste and add a little flaky sea salt only if needed. Serve hot.