Sweet potato casserole with pistachio crust

Peel the sweet potatoes and cut into cubes of about the same size so they cook evenly.

Put in a pot with water and a big pinch of salt; boil on high heat until just tender when tested with a knife or skewer.

Drain well, return to the pot with the butter, mash and set aside.

Mix the eggs, maple syrup, vanilla, cayenne, allspice, salt, buttermilk and milk.

Add the mashed sweet potatoes a spoonful at a time, mixing after each, to raise the temperature of the eggs slowly so they do not curdle; then add the rest and mix.

Transfer into a lightly buttered two and a half quart casserole dish, leaving room for the topping.

Chop the pistachios; mix with light brown sugar, flour and melted butter until completely combined.

Crumble the topping evenly over the top by hand, then press it gently down with the back of a fork.

Bake at 350 for about 25 to 30 minutes, until the top is browned and the sweet potato is set.

Optional: broil for about a minute at the end to caramelize the crust a little more.

Let rest a little while before serving.