Chef John's Classic Shepherd's Pie

Begin by placing the cubed potatoes and minced garlic in a large container with sufficient water to submerge them completely. Bring the mixture to a rolling boil over extremely high heat, then gradually decrease the intensity to a low-medium flame, cover the pot, and let it simmer until the potatoes are tender, approximately 20 minutes.

In a separate area, preheat your oven to 375 degrees Fahrenheit (190 degrees Celsius). At the same time, cook ground beef over a medium heat in a skillet. Gradually incorporate flour into the mixture, allowing it to blend seamlessly with the beef's natural juices. Introduce beef broth, ketchup, vegetables, salt, and pepper into the skillet, stirring everything together. Continue cooking until the mixture thickens, roughly 5 minutes. Transfer this meat mixture to an oven-safe casserole dish.

Drain the cooked potatoes and slightly mash them before adding 1/4 cup of grated cheese and sour cream. Combine the ingredients until they form a smooth, uniform mixture.

Layer the meat mixture with the mashed potatoes in the casserole dish. Spread the potatoes from the center of the dish outwards, forming a uniform layer along the edges. Sprinkle the remaining 1/4 cup of grated cheese over the top.

Bake the casserole in the preheated oven until the cheese melts and turns a golden hue, approximately 20 to 25 minutes. Allow it to cool for 15 minutes before serving.