1) Toss the fontina and gruyere cheese with the cornflour in a medium bowl to coat. Saute the pancetta in a heavy large saucepan over medium heat until crisp and golden, about eight minutes.
2) Using a slotted spoon, transfer the pancetta to a plate. Pour off any excess oil.
3) Pour the wine into the same saucepan and bring to a boil. Decrease the heat to medium. Whisk one handful of the cheese mixture into the wine until it is almost melted. Repeat with the remaining cheese mixture in about four more batches. Continue whisking until the cheese is completely melted and the fondue bubbles, about one minute. Stir in all but two tablespoons of the pancetta. Season the fondue with pepper, to taste.
4) Transfer the cheese mixture to a fondue pot. Sprinkle with the remaining pancetta and chives. Set the pot over a candle or a canned heat burner.