Microwave peanut butter and butter in large microwavable bowl on HIGH 4 minutes, stirring after 2 minutes. Add confectioners’ sugar, vanilla and cinnamon; mix until smooth.
Spoon into foil-lined 8-inch square baking pan. Sprinkle with pretzels, pressing gently into fudge. Drizzle with melted chocolate.
Let stand at room temperature 2 hours or until firm. Use foil to lift out of pan onto cutting board. Cut into 36 pieces. Store in tightly covered container at cool room temperature.