It’s an homage to Arnold’s Country Kitchen, where squash casserole is a favorite. This version has a base of sour cream, white cheddar, and a touch of mayonnaise bubbling up into squash scattered with ribbons of pimiento. Then comes a rich row of deeply caramelized onions and a crispy dusting of buttered bread crumbs and parsley.
Ingredients
- 2½ tablespoons butter, plus more for pan
- 3 onions, halved and thinly sliced
- ¼ cup (60 ml) balsamic vinegar
- 1¼ teaspoons sea salt
- 1 tablespoon extra-virgin olive oil
- 7 medium yellow squash, sliced
- ¾ cup (180 ml) sour cream
- ¼ cup (60 ml) mayonnaise
- 1 cup (120 g) shredded sharp white cheddar cheese
- 3 tablespoons prepared plain bread crumbs
- 2 tablespoons chopped fresh parsley
- 1 (4-ounce/113-g) jar of sliced pimientos, drained
How to Make It
- Preheat the oven to 350°F (175°C) and butter a baking dish.
- In a large skillet, melt 1½ tablespoons of the butter over medium-high. Add the onions. They’ll begin to soften after about 10 minutes, and after about 20 minutes, you might need to turn down the heat. Continue cooking them for 40 minutes to an hour, until they are brown. Add the vinegar and stir to scrape up any dark bits on the bottom of the pan. Season with ¼ teaspoon of the salt. Set the onions aside.
- In another large skillet, heat the oil over medium-high, then sauté the squash until it is beginning to soften but not yet losing its shape. Season it with 1 teaspoon salt. Set the squash aside.
- In a small bowl, combine the sour cream, mayonnaise, and cheese. Melt the remaining 1 tablespoon butter and pour it into a second small bowl; stir in the bread crumbs and parsley.
- Assemble the casserole by layering the sour cream mixture on the bottom of the prepared dish, then the squash, then a scattering of pimientos, then caramelized onions and the bread crumb mixture. Bake for 25 to 30 minutes or until the casserole is hot and bubbly. Allow it to cool for 10 to 15 minutes to make it easier to slice and serve.
