Render Bacon: In a Dutch oven, cook diced bacon over medium-low heat for about 20-25 minutes until crispy and golden, stirring occasionally.

Caramelize Onions: Using the same pot with the bacon fat, add sliced red onions and cook for 5-6 minutes until tender and caramelized, stirring in chopped scallions and kosher salt until fragrant.

Sauté Vegetables: Drizzle olive oil into the pot and add halved Brussels sprouts, sautéing until browned (4-5 minutes), then remove and cook chopped kale until wilted (2-3 minutes).

Prepare Breadcrumbs: Process cooked bacon and some bread into coarse crumbs, fry them in olive oil until golden and crisp.

Cook Pasta: Bring large pot of salted water to boil and cook conchiglioni according to package instructions (10-12 minutes), drain and set aside, reserving a bit of pasta water.

Make Cheese Sauce: Melt butter, whisk in flour, then gradually add warm milk, stirring until thickened. Stir in shredded cheddar cheese until smooth.

Combine: Add drained pasta, sautéed Brussels sprouts and kale to the cheese sauce, folding together and adjust consistency with reserved pasta water if needed, season with salt.

Serve: Dish out portions topped with crispy bacon breadcrumbs and fresh chives. Best enjoyed warm.