Beef Cottage Pie with Rutabaga Mash

Ingredients

• 2 lb rutabaga (about 1 large), peeled and cut into 1-inch cubes
• 1 1/2 tsp fine sea salt, divided
• 3 tbsp olive oil, divided
• 1 medium yellow onion, finely chopped
• 3 stalks celery, finely chopped
• 4 cloves garlic, minced
• 2 tsp fresh thyme leaves
• 1 1/2 lb ground beef
• 1 3/4 cups beef bone broth, divided Label: beef bones, water, vegetables, herbs, and salt, with no sugar, natural flavors, or oil
• 1 dried bay leaf
• 2 packed cups chopped kale leaves, stems removed
• 1 tbsp apple cider vinegar
• 2 tbsp chopped fresh chives

Instructions

1. Boil the rutabaga: Put the rutabaga cubes in a large pot, cover them with cold water by an inch, add 1/2 teaspoon of the salt, and bring to a boil. Simmer for 25 to 30 minutes, until a knife slides through a cube with no resistance. Rutabaga stays firm long after a potato would be done, so test it with the knife rather than going by the clock. Starting in cold water heats the cubes through evenly, so the centers soften by the time the outsides do.
2. Soften the vegetables: While the rutabaga boils, heat 1 tablespoon of the olive oil in a large (12-inch) skillet over medium heat. Add the onion and celery and cook for 7 minutes, stirring now and then, until soft and translucent. Add the garlic and thyme and cook 1 minute more, until you can smell the garlic. Cooking the onion and celery slowly draws out their sweetness, which becomes the base of the gravy.
3. Brown the beef: Raise the heat to medium-high, add the beef and 1/2 teaspoon of the salt, press it into an even layer over the vegetables, and let it cook undisturbed for 4 minutes, until it browns on the bottom. Break it into crumbles and cook 3 to 4 minutes more, until no pink remains and it reaches 160°F (71°C). The browned bits on the beef and the bottom of the pan are where the gravy gets its depth.
4. Simmer the filling: Heat the oven to 400°F (200°C). Pour 1 1/2 cups of the broth into the skillet, scrape up the browned bits, and add the bay leaf. Simmer for 12 to 15 minutes, stirring now and then, until the liquid reduces to a thick gravy that coats the beef and a spoon dragged through the pan leaves a trail. Stir in the kale and cook 3 minutes more, until it wilts and turns bright green. Take out the bay leaf and stir in the vinegar. A thick filling holds the mash up on top, where a thin one lets it sink.
5. Mash the rutabaga: Drain the rutabaga well and return it to the dry pot over low heat for 1 minute, shaking the pot, to steam off the last of the water. Take it off the heat, add the remaining 2 tablespoons of olive oil, the remaining 1/4 cup of broth, and the remaining 1/2 teaspoon of salt, and mash by hand until thick and mostly smooth. Rutabaga holds more water than potato, and drying it is what keeps the topping thick enough to brown.
6. Assemble: Spread the filling in a 2-quart baking dish and level it. Spoon the mash over the top in dollops, then spread them together gently with the back of the spoon so the filling stays underneath. Drag a fork across the surface to raise ridges all over; the ridges are the edges that brown in the oven.
7. Bake: Bake for 25 to 30 minutes, until the ridges are golden brown and the filling bubbles at the edges. Let it stand for 10 minutes so the layers set enough to serve in squares, then scatter the chives over the top.