In a large heavy skillet, render the bacon until crispy.
Remove the bacon from the pan and drain on paper towels, leaving the fat in the pan.
Whisk in the flour to make a roux and cook 2-3 minutes.
Whisk in the milk, stirring constantly, until the gravy comes to a boil.
Reduce the heat to low and simmer for 15-20 minutes.
While the gravy is cooking, cook French fries by desired method on the package.
To serve: Place hot French fries on a large platter. Top with a generous amount of the gravy, then the cheese. Top with bacon and scallions. Serve immediately.