Heat oil to 300 degrees in a heavy duty pot or deep fryer.
After the fries have been peeled and cut, place in a bowl of ice water for 5 minutes, then drain, rinse the fries, and dry them.
Add the potatoes to the oil and cook for 4 minutes.
Transfer to a paper-lined towel baking sheet. Place in fridge and heat oil to 375 degrees. And begin the cheese sauce.
Melt butter in a small saucepan over medium heat. Whisk in flour and cook for about 30 seconds.
Slowly pour in milk, whisking constantly. Allow the sauce to thicken, about 3-4 minutes. Add in the mustard and stir.
Reduce heat to low and add in cheese 1/2 cup at a time to allow each batch to completely melt while stirring. Keep sauce warm while fries cook again.
Add the fries again to the oil and cook until golden brown and crispy, about 3-4 minutes.
Place fries on a serving platter and pour cheese sauce on top. Garnish with bacon and chives.