"It's like a better version of scalloped potatoes...."
butter, plus more for pan
small yellow onion, finely chopped
all-purpose flour
sweet paprika
whole milk
Kosher salt
Freshly ground black pepper
diced cooked ham
russet potatoes, peeled and sliced into 1/4"-thick rounds
shredded cheddar
Freshly chopped chives, for serving