Heat the oven to 160C/320F/gas mark 2½. Put the potatoes in a medium pot and cover with cold water. Bring to a boil and cook for six to eight minutes, just until tender. Strain, refresh under cold water, then drain and pat dry with a clean towel.
In a large bowl, whisk the eggs, milk, cream, half a teaspoon of salt and half a teaspoon of black pepper.
Grease a 22cm, high-sided, round ovenproof dish with some melted butter. Lay a third of the potatoes on the base and spread over half the salmon and half the dill. Top with another third of the potatoes, then more salmon and dill, followed by the rest of the spuds. Pour over the custard and grind pepper on top.
Bake for 45 minutes, or until the custard is set (a knife should come out dry). Remove from the oven and brush with melted butter. Leave to sit for at least 10 minutes before serving warm.⏱ 45 min