1. Position a rack in the top third of the oven and preheat to 350°F. Spread the walnuts out on a baking sheet. Bake, stirring occasionally, until the walnuts are fragrant and lightly toasted, 10 to 12 minutes. Cool completely. Finely chop the walnuts, either in a food processor fitted with the metal chopping blade or by hand; set aside.

2. In a medium, heavy-bottomed saucepan, melt the butter over medium heat. Add the shallots and cook, stirring often, until softened, about 2 minutes. Add the port wine and lemon juice and bring to a bare simmer.

3. In a medium bowl, mash the Gorgonzola cheese with the cornstarch until well combined. In four or five additions, stir the cheese into the saucepan, stirring until the previous addition is melted before adding another. Allow the fondue to come to a bare simmer, but do not boil. Season with the pepper.

4. Transfer the fondue to a ceramic or enameled iron fondue pot and keep warm over a fondue burner. Serve immediately, with dipping ingredients of your choice and small bowls of the chopped walnuts, so guests can dip their fondue-covered food into the walnuts before eating.