No-Fail Pistachio and Walnut Fudge

Line an 8-inch baking dish with aluminum foil (a 12 x 12 square works perfectly). Spray with nonstick spray.Combine milk and dark chocolate with condensed milk in a large saucepan over low to medium heat. Cook, stirring constantly, until the chocolate melts and the mixture is smooth. Remove from heat and stir in vanilla and pistachios. Immediately spread fudge in prepared baking dish and smooth the top with an offset spatula. Press in the walnuts on top. Refrigerate until firm (2 hours) and lift the fudge out of the baking dish with the foil. Rove foil completely and cut into 1" squares with a very sharp knife.