Greens and Cheese Strata

From the garden

• 1 lb chard, kale, komatsuna, or another sturdy cooking green, washed, tough stems stripped out, leaves chopped
• 1 medium yellow onion, diced

From the pantry

• 8 cups day-old crusty bread, cut into 1-inch cubes · about a 12-ounce loaf; slightly stale is ideal
• 8 eggs
• 2½ cups milk
• 6 oz sharp cheddar, shredded · Gruyère is the classic if you have it
• 2 tbsp olive oil
• 1 tsp Dijon mustard
• 1 tbsp butter · for the baking dish
• ¾ tsp salt
• ½ tsp black pepper

1. Warm the olive oil in a wide skillet over medium heat and cook the onion 5 minutes until soft. Add the greens in batches with a pinch of salt and cook until fully wilted and their liquid has cooked off, 5–8 minutes. Cool slightly, then press or squeeze out any remaining moisture. Wet greens make a soggy strata.
2. Butter a 9x13-inch baking dish. Layer in half the bread cubes, half the greens, and half the cheese; repeat with the rest.
3. Whisk the eggs with the milk, Dijon, salt, and pepper and pour evenly over the dish. Press down with a spatula so the bread starts drinking up the custard.
4. Cover and refrigerate at least 1 hour and up to overnight. The long soak is what makes it custardy instead of dry.
5. Bake uncovered at 350°F for 45–55 minutes, until puffed, golden, and just set in the center (a knife should come out without wet custard).
6. Rest 10 minutes before cutting into squares; it slices cleanly once it settles.