We try to stick with strictly Italian flavors when we’re thinking up dishes for the restaurants, but I can promise that you will never find anything like these crostini in Italy. It’s basically an assemblage of Thanksgiving flavors, or flavors of the American south, on toast.
I let it slide in terms of our Italian paradigm because the flavors are just so comforting and delicious. I recommend you make this only in the fall when the butternut squash, at least that which you’ll find at farmers markets, has flavor. When good squash isn’t available, we make the purée using orange-fleshed sweet potatoes, and we suggest you do the same.
Preheat the oven to 350 degrees. Adjust the oven rack to the middle position.
Place the bread slices on a baking sheet, brush the tops with olive oil, and bake them for 15-20 minutes, until lightly toasted and golden brown. Remove from the oven and rub the oiled side of the crostini with the garlic.
Increase the oven temperature to 375 degrees.
Cut the butternut squash in half and scoop out and discard the seeds. Season the cut sides liberally with salt and pepper, drizzle each half with 1 tablespoon of the olive oil, and use your fingers to rub it all over the flesh. Place the squash cut side down in a baking dish or on a baking sheet and place it in the oven to roast until it is mushy tender, about 45 minutes.
Place the bacon on a baking sheet and bake it simultaneously with the squash until it is cooked all the way through but not crisp, 15-17 minutes. Remove the bacon from the oven and transfer it to paper towels to drain.
When the squash is cool enough to handle, use a wooden spoon or rubber spatula to scrape the flesh out of the skins. (Avoid using a metal spoon; this helps prevent taking the skin with you when you are scraping out the flesh, which you don’t want in the purée.) Discard the squash skin and pass the flesh through a food mill into a medium-sized saucepan.
Cook the squash purée over high heat for 5 minutes to cook out some of the moisture, stirring constantly to prevent it from sticking to the pan.
Meanwhile, place the butter in a medium-sized saucepan and cook it over medium-high heat without stirring, swirling the pan occasionally to brown the butter evenly so that it doesn’t burn, until the bubbles subside and the butter is dark brown with a nutty, toasty smell, 3-5 minutes.
Turn off the heat and pour the butter into the saucepan with the butternut squash. Add the sugar and several gratings of fresh nutmeg, season with salt, and stir to thoroughly combine the ingredients. Taste for seasoning and add more salt, sugar, or nutmeg if desired.
To prepare the greens, tear the radicchio into large pieces. Heat the remaining olive oil in a large sauté pan over high heat until it is almost smoking; the oil will slide easily in the pan. Add the radicchio, frisée, and arugula, season them with salt and pepper, and sauté for about 2 minutes, or until they begin to wilt.
Turn off the heat, add the shallots and vinegar, toss to coat the greens with the seasonings, and cook the vinegar from the residual heat in the pan for about 1 minute. Taste the greens for seasoning and add more salt or pepper, if desired.
To assemble the crostini, lay the bread slices oiled side up on a work surface. Drape a thin layer the greens on top of each of the crostini, leaving the edges of the bread visible. Spoon a heaping tablespoon of the squash purée on top of the vegetables, leaving the greens visible around the edges. Cut each slice of bacon in half crosswise on the bias, lay one half on top of each crostino at an angle, and serve.