PREP: Set out and measure all the ingredients. Set out a whisk. Line a rimmed baking sheet with parchment paper or a silpat baking mat and set both right next to the stovetop.
BAKING SODA: Sprinkle the baking soda through a fine mesh sieve into a little bowl. This is important so there aren't any clumps of baking soda. Set next to the stovetop along with the vanilla extract and salt.
MAKE THE CANDY: In a large and solid heavy-bottomed pot (the bigger the better, this candy will triple in size!) add the sugar and water. Stir to combine. Turn the heat to medium high and then add in the corn syrup. Stir to incorporate and then leave the mixture to boil. Do not stir the mixture while boiling, this could trigger the sugar to crystallize.
BOIL: Insert the candy thermometer and continue to heat, without stirring, until the mixture reaches 300 degrees F (150 degrees C). Watch carefully, it can jump up to temperature in an instant even though it may seem like it is moving slowly! Do not increase the temperature to speed up the process.
ADD BAKING SODA, SALT, & VANILLA: As soon as the temperature hits 300 degrees F, remove pan from heat and, working very quickly sprinkle the baking soda, vanilla, and salt evenly over the candy. Quickly and vigorously whisk into the sugar syrup (whisking for no more than 5-10 seconds–to prevent deflating the candy). The mixture will begin to expand and triple in size. Quickly pour the candy onto the prepared pan and leave it to expand on it's own (do not spread). Don't touch or move the candy for 1 hour.
BREAK CANDY: Once the candy has cooled and set, remove it from the pan and using a blunt object like a meat mallet or handle of a chef's knife) shatter the candy into bite size pieces. Alternatively, break up the candy with your hands.
OPTIONAL -- ADD CHOCOLATE: Melt chocolate in a microwave safe bowl. Heat in bursts of 30 seconds, stirring in between each burst for 15-20 seconds. Heat for a total of 1 minute to 1 minute and 15 seconds. IF desired, add in 1/4 teaspoon vegetable oil or shortening to slightly thin the chocolate. Dip individual honeycomb pieces in the melted chocolate OR drizzle pieces with chocolate. Place dipped or chocolate covered candy on a parchment paper lined baking sheet and let stand at room temperature until chocolate is hardened, about 1 hour.
STORAGE: store in an airtight container in a very dry place. Alternatively store in the freezer. Best eaten within 1 week. Honeycomb will become soft and chewy in a humid environment. Do not refrigerate.