For the dip, combine the cheese and cornstarch in a large bowl, toss to coat and set aside.
In a heavy-bottomed saucepan over medium heat, add the oil, garlic, shallots, and rosemary. Season with a pinch of salt and cook until the shallot and garlic soften slightly, about 1 minute.
Add the wine and simmer, about 1 minute. Whisk in the cream, pepper and cayenne pepper. When the cream mixture begins to bubble, remove from the heat and strain over the blue cheese, whisking to incorporate.
Remove from the heat and stir in the chives if using.
For the crisps, in a medium pot, pour enough oil so that the oil comes 3 inches up the sides. Heat over medium heat until a deep-frying thermometer inserted in the oil reaches 170°C. (If you don't have a thermometer, a cube of bread will brown in about 3 minutes.)
Slice the potatoes thinly on a mandolin. As you slice them, put them in a bowl of cold water to cover.
Drain the potatoes and pat dry. Working in batches if necessary, cook the potatoes in the oil until they are golden brown and crispy, about 3 minutes.
Add the garlic if using, along with the potatoes. Remove the potatoes from the oil to a large paper towel-lined bowl and season them with the rosemary and salt, shaking the bowl to distribute the seasoning evenly.