Step 1

Start with the mayonnaise. Put the egg yolks, mustard and vinegar into a medium mixing bowl. Using an electric handheld mixer, beat everything together for 1 minute until well combined.

Step 2

Slowly drizzle in the oil, whisking constantly. It should start to thicken after you’ve added around a third. If not, stop adding oil and beat until it thickens a little, then continue. Once two-thirds of the oil has been added and the mixture is thickening, start adding the oil a bit more quickly. If at any point it develops a greasy sheen on top, whisk in a little cold water, then continue.

Step 3

Once all the oil is added, you should have a thick, spoonable mayonnaise that holds its shape in the bowl. Taste and add more seasoning, mustard or a splash more vinegar if liked – it should be tangy and mustardy, but balanced. Set aside.

Step 4

Put the eggs into a saucepan, pour over just-boiled water from the kettle and set the pan over a high heat. Boil for 7 minutes, then drain the eggs and submerge briefly in cold water to stop them cooking, without cooling them down

Step 5

Meanwhile, put the herbs, capers, salad onions and 6 tbsp mayonnaise into a bowl. Once the eggs are cool enough to handle, peel, then roughly chop. Stir them through the mayo mixture with plenty of seasoning. Divide between the buttered toasted muffins and top with a handful of salad leaves. Serve with a lemon wedge on the side for squeezing over.