Bake the French fries according to package directions. Meanwhile, melt the butter in a medium-size saucepan over medium heat. Once the butter has melted whisk in the flour. Cook for 2 minutes while whisking.
Pour in the milk and stir while whisking. Continue cooking until the sauce becomes slightly thick. Add the cheese and stir until it is melted and the sauce is thick. Remove from heat.
Top the cook French fries with diced ham, diced pickle, and drizzle with cheese sauce and mustard.