In a medium, heavy-bottomed saucepan melt the butter over medium heat. Add the mushrooms and cook, stirring often, until golden brown and most of their liquid has evaporated, about 5 minutes. Add the shallots and cook until softened, about 1 minute. Add the wine and bring to a simmer.

Reduce the heat to medium-low. In a medium bowl, combine the cubed fontina with the cornstarch and toss to mix well. Add the cheese-cornstarch mixture to the saucepan in 3 additions, stirring constantly and adding more cheese only as the previous batch has completely melted. Stir in the grated Truffled Pecorino Romano and allow the fondue to come to a bare simmer but do not allow to boil. Season with pepper and transfer to a fondue pot for serving.

Serve, with dipping items of choice, attractively arranged in separate bowls.