- Preheat oven to 375 degrees. In a large skillet or high-sided sauté pan, melt ¼ cup butter over medium-low heat and add breadcrumbs to pan. Toast breadcrumbs, stirring constantly, until deep golden-brown, about 5 minutes. Transfer toasted breadcrumbs to a paper towel-lined plate and wipe any remaining crumbs from the pan.
- Add remaining 2 tablespoons butter to pan and sauté shallots over medium heat until soft. Add flour to pan, stir, and cook for 1 minute. Add chicken stock, stirring constantly, and bring to a boil. Reduce heat to low and add butterbeans to pan. Stir to combine and leave pan on heat until beans are just warmed through.
- Remove pan from heat, stir in sour cream, and season with salt and pepper. Transfer to a casserole dish, top with toasted breadcrumbs, and bake for 40 minutes or until bubbling.