Step 1Line a rimmed baking sheet with greased parchment paper or a silicone baking mat.
Step 2In a large, heavy-bottom saucepan, combine the sugar, honey, corn syrup and water and bring the mixture to a boil over medium-high heat. Continue cooking until a candy thermometer reaches 300 degrees, then slowly whisk in the baking soda (be careful, the mixture will bubble dramatically and increase to approximately 4 times its original volume).
Step 3Pour the mixture onto the baking sheet and set the sheet aside until the honeycomb is cooled to room temperature, about 30 minutes.
Step 4While the honeycomb is cooling, melt the chocolate. Place the chocolate in a bowl set over a simmering bowl of water, stirring, until the chocolate is melted; alternatively, melt the chocolate in batches in a glass bowl in the microwave, stirring every 10 seconds or so until the chocolate is fully melted.
Step 5Break the honeycomb into bite-sized pieces. Using two forks, carefully dip each piece in the melted chocolate to coat, gently shaking each piece to remove the excess chocolate. Place the pieces on a parchment- or silicone-lined baking sheet to cool. If desired, sprinkle the freshly coated honeycomb with chopped nuts for decoration. Store the pieces on parchment or wax paper in an airtight container in a cool, dry place.