Toss the shredded cheese with the cornstarch in a mixing bowl. Make sure the cheese is well coated with the cornstarch. Set the cheese aside.
Combine the Sauvignon Blanc, Sherry, lemon juice, nutmeg, and mustard in a small bowl. Whisk to combine and set aside.
Melt the butter in a large saucepan over medium heat. Add the onion and saute for 5-7 minutes, or until golden.
Add the garlic and stir for 30 seconds.
Add the wine and sherry mixture to the onions and garlic. Bring the mixture to a boil, and then reduce the heat to low.
Add the cheese to the saucepan one handful at a time. Stir continuously until the cheese is melted, and then add the next handful. Make sure the stove is warm enough to melt the cheese, but low enough so that it doesn't burn or clump.
Once all of the cheese is melted and smooth, stir in the herbs. Pour the fondue into a fondue pot or a glass container that can be rewarmed in the microwave periodically.
Serve the fondue with roasted vegetables: red potatoes, roasted broccoli, cauliflower, asparagus.