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["Toast walnuts on a baking sheet at 350 degrees for 6 minutes.", "Chop roughly and set aside.", "Line an 8"" square baking pan with foil, pressing the foil into the corners and leaving a 2"" overhang on two opposite sides.", "Melt the chocolate and butter in a large heatproof bowl set over a pan of barely simmering water, about 5 minutes, stirring constantly.", "When the chocolate is almost fully melted, remove the bowl from the heat and stir to melt the remaining pieces.", "Let cool at room temperature for 5 minutes.", "Stir in 1 cup of the marshmallows, 1 cup of the walnuts and all graham cracker pieces.", "Spread the mixture into the prepared pan.", "Sprinkle with remaining 1/2 cup of marshmallows and 1/4 cup of walnuts, pressing down lightly to adhere.", "Let stand at room temperature until the chocolate sets, about 2 hours, or 1 hour in refrigerator.", "Grab foil overhang to lift the set mixture out of the pan, and place on a cutting board.", "Peel the foil from the sides.", "Using a bench scraper or a sharp knife, cut into small squares (20-30 depending on desired piece size).", "Store, layered between sheets of wax paper in an airtight container for up to 1 week, or refrigerate up to 3 weeks."]
