Black Walnut Jersey Candy

2 1/2 cups brown sugar, firmly packed
8 tablespoons butter
1/2 cup very heavy cream or whipping cream
1 cup black walnuts

Combine the sugar and cream, and bring to a boil over high heat, stirring constantly. Reduce the heat, add the butter and stir until it melts. Remove from heat, add walnuts, and beat until thick and creamy. Pour into a greased tray, let set until firm, then cut into squares and serve.