1. Cut potatoes lengthwise in 1/4-inch squares. Soak cut potatoes in water for 1 hour to remove starch. Heat oil to 325 degrees F and blanch potatoes for 5 minutes until very soft but not brown. Remove from oil. Drain on paper towels.
2. In a medium saute pan over medium heat, cook bacon until just crisp, taking care not to overcook. Drain on paper towels.
3. In a 2 quart saucepan, melt butter over medium heat. Add onion and cook about 2 minutes. Add garlic and flour, whisk until smooth. Cook 2 minutes more. Add chili sauce and mustard, and slowly whisk in heavy cream. When mixture begins to simmer, add cheeses and remove from heat. Taste sauce for seasoning. If sauce is too thick, thin with more cream. If too thin, thicken with a little more cheese.
4. Increase oil temperature to 375 degrees F. Fry potatoes a second time until crisp and golden brown. Remove from oil and drain again, season with salt immediately. On a large plate, arrange fries in the center, drizzle with sauce, top with crumbled bacon and chives. Serve immediately.
Recipe courtesy of Adam Gertler