Line a baking tray with parchment paper and set aside.
In a heavy bottom pot add the sugar, corn syrup and water. Heat on medium and stir until the sugar is dissolved and starts to bubble. Use a wood or metal spoon to stir the mixture. A plastic or silicon spoon may melt when stirring as the temperature increases.
Add the sesame seeds and stir. Continue stirring until it turns a golden color, about 7-10 minutes. It should smell like toasted sesame seeds. If using a candy thermometer it should read 300℉.
Remove the pot from the heat and add the butter and miso. It will bubble up slightly. Continue to stir until it's incorporated.
Add the baking soda and stir. This will cause it to foam up a bit.
Pour the mixture onto the lined baking sheet and smooth out. Make sure not to touch it because it's very hot!
Let it cool for about 30 minutes. It may take longer depending on the humidity.
Once it's hardened break it into pieces. They are best stored in a sealed container in a cool, dry place. They can stick together if piled on top of each other so use parchment paper to layer them. If it's humid they may get sticky and soft. The fridge may create moisture causing them to get slightly sticky as well. They're best eaten within 1 week. Enjoy!
Notes
*Honey can be used instead of corn syrup. I have not tried using maple syrup but I think that it should work as well.*Light or dark miso can be used. Light miso will give a lighter flavor and dark miso a stronger flavor. *To clean your pot, simply soak it in hot soapy water for 1-2 hours and the hardened candy will dissolve.