Preheat oven to 350°F.

Cut @potatoes{1.5%lbs} into thin slices.

Heat @unsalted butter{1/4%cup} in #saucepan{}; sprinkle with @flour{3%Tbsp}, and cook for ~{2%minutes}. Add @milk{2.5%cups}, @salt{1/2%tsp}, and @pepper{1/4%tsp}. Simmer until boiling. Remove from heat.

In a #casserole dish{}, layer potatoes and @broccoli{3%cups}. Top with white sauce.

Cover and bake for ~{15%minutes}, then an additional 5 uncovered.