Ingredients
- 3 pounds russet potatoes peeled and quartered
- 10 tablespoons unsalted butter divided
- 1/2 large onion diced
- 4 medium celery ribs diced
- 2 slices white bread cubed
- 1 cup milk
- 1 large egg beaten
- Kosher salt to taste
Instructions
- Preheat the oven to 350°F. Grease a 9x13-inch casserole dish.
- Place quartered potatoes in a large pot of salted water. Bring to a boil, then reduce to a simmer until tender, about 15 minutes. Drain and set aside.
- In a skillet, melt 4 tablespoons butter over medium heat. Add diced onion and celery, cooking until soft and golden, about 20 minutes.
- Toast the bread cubes lightly until golden.
- Mash the potatoes and mix in the sautéed vegetables, toasted bread cubes, remaining butter, milk, and beaten egg. Season with salt. Transfer to the prepared dish and bake for 45 minutes until golden brown.
