1. Preheat oven to 425°F, with a rack in top position. Boil a large pot of salted water. Add macaroni, cooking until al dente, 6 to 8 minutes. Strain.
2. In a large saucepan, cook bacon until browned, about 5 minutes. Add garlic and kale and cook until wilted, about 3 more minutes. Season with salt and pepper. Transfer to baking dish.
3. Wipe saucepan clean. Place over medium heat; add butter. Once melted, whisk in flour to create a roux. Once it’s a paste, add half-and-half and milk. Turn heat to low, and cook until slightly thickened, about 8 minutes. (Be sure not to let it get too thick.) Add sour cream and all but ½ cup cheese. Pour cheese sauce into cooked pasta; add kale-bacon mixture, and stir to incorporate.
4. Transfer cheesy pasta to baking dish. Sprinkle remaining cheese on top, followed by panko. Bake until browned and bubbling, 15 to 20 minutes.