Make sure the butter is fully softened then grate the garlic and zest the lime. Heat oil in a frying pan over a medium heat. Fry off the curry paste in some oil along with the garlic for 2 mins, then take off the heat and cool. Mix with the butter, lime zest (and a pinch of salt if using unsalted butter).

Finely slice the red onion and put into a bowl with the lime juice and a pinch of salt. Give it a little massage to soften up, and set aside.

Finely chop the chilli. Heat a grill to medium-high and slice the cheddar — don't be tempted to grate it! The cheese will split when it's mixed with the melted butter (trust us, we've tried it). Toast crumpets then pop onto a baking tray, spreading with the butter and topping with cheddar and Parmesan, if using. Slide under the grill and cook until bubbly and golden. Bring them out and top with the pickled onions, chilli and nigella seeds.

Pop any leftover butter into an airtight container and put in the fridge.