Ragù cottage pie

Uses 3½ cups of Sunday's ragù (move it from the freezer to the fridge Tuesday night)

Ragù and peas under a thick parmesan mash, baked until the ridges brown. The best thing to happen to the last of the pot.

55 min (25 min hands-on) · serves 4

You need

• 3½ cups ragù (from Sunday, thawed)
• 1 cup frozen peas
• 2½ lb Yukon Gold potatoes, peeled and cut into 2-inch chunks
• 1 tbsp kosher salt, for the water
• ½ cup whole milk, warmed
• 4 tbsp unsalted butter
• 1 egg yolk
• ½ cup grated parmesan
• Salt and black pepper

How to make it

1. Heat the oven to 400°F. Put the potatoes in a pot, cover with cold water by an inch, add the 1 tbsp salt and bring to a boil. Simmer 15 to 18 minutes, until a knife slides through a chunk with no resistance.
2. Drain well and let them steam in the colander 2 minutes so the mash isn't watery. Mash in the pot with the warm milk and butter until smooth, then beat in the egg yolk and half the parmesan. Taste for salt and pepper.
3. Stir the frozen peas into the ragù and spread it in a 2-quart baking dish (8 by 8 or a deep pie dish).
4. Spoon the mash over the top, starting at the edges so it seals in the sauce, then spread it and rough up the surface with a fork. The ridges are what brown. Sprinkle with the rest of the parmesan.
5. Set the dish on a sheet pan and bake 25 minutes, until the sauce bubbles up at the edges. Then broil 2 to 3 minutes, watching, until the top is deep golden in places.
6. Let it rest 5 minutes so it holds together when you serve it.

The egg yolk makes the top brown and crisp. Leave it out if you like and it's still very good.