You can make this a day ahead, if desired and the flavors will develop overnight. Reheat, covered for about 20 minutes. I use this as a side dish for pork tenderloins or for "Flashkarre" (see pork recipes).
Position a rack in the center of the oven and heat the oven to 400 degrees. Rub a 2-quart shallow gratin dish with 1/2 tsp. of the butter.
In a 12-inch nonstick skillet over medium heat, cook the bacon until crisp, about 8 minutes. Transfer the bacon to paper towels. Reserve 2 T. fat in the skillet; discard the remainder. When the bacon is cool, crumble or mince it.
In a small bowl, combine 1 T. of the crumbled bacon with the breadcrumbs, 2 T. of the cheese, the olive oil, 1/2 tsp. of the thyme and a large pinch of salt. Mix well.
Add the remaining 1 T. butter to the skillet with the bacon fat and melt over medium heat. Add the leeks and a pinch of salt and cook, stirring until softened and just starting to turn golden, 6-7 minutes. Add the garlic and stir well. Add the corn, 1/4 tsp. salt and a few grinds of pepper. Cook stirring until the corn has lost its raw look and is slightly shrunken, 2-3 minutes. Cool slightly.
Combine the cream and chicken broth in a 2-cup liquid measure. Add 1/2 tsp. salt and a few grinds of the pepper; stir to mix well.
In a large bowl, combine the remaining bacon, the corn-leek mixture, the diced squash, potatoes and remaining 1 tsp. thyme. Toss lightly to combine. Spread the mixture evenly in the gratin dish and sprinkle the remaining 1/2 cup cheese on top. Stir the cream mixture one more time and pour it over everything as evenly as possible. Be sure to scrape out any seasonings left in the cup. Press down on the vegetables with a spatula so that the liquid surrounds them and everything is evenly distributed. Sprinkle the breadcrumb mixture over all. Cover with foil and bake for 20 minutes. Remove the foil and continue to bake until the crumb topping is deeply golden and the squash and potatoes are tender when pierced with a fork, about 25 minutes. The liquid should have bubbled below the surface of the vegetables, leaving brown bits around the edge of the pan. Let cool for 15-20 minutes before serving if desired. Serves 6-8 generously.
1 T. plus 1/2 tsp. unsalted butter
4 slices bacon
1 1/2 cups fresh breadcrumbs
1/2 cup plus 2 T. grated Parmigiano-Reggiano cheese
1 T. extra-virgin olive oil
1 1/2 tsp. chopped fresh thyme leaves
1 large or 2 medium leeks (white and light-green parts only, halved and sliced 1/4 inch thick
2 tsp. minced fresh garlic
1 3/4-2 cups fresh corn kernels (3-4 large ears)
Freshly ground black pepper
2/3 cup heavy cream
3/4 cup lower-salt chicken broth
12 oz. peeled and seeded butternut squash, cut into 1/2 inch dice (about 2 1/2 cups)
8 oz. Yukon Gold potatoes, cut into 1/2 inch dice (about 1 1/2 cups) (I did not peel them)