Line an 8" square pan with parchment paper. Set aside.
Combine the cream, vanilla extract, and espresso powder in a medium-sized saucepan and heat while swirling until scalding. As soon as the mixture starts to bubble and appears to coat the bottom of the pan, you'll know its done. Remove from the heat, add the chopped chocolate and allow to sit for a minute to allow it to melt. Then, stir until it turns into a completely smooth mixture. Stir in the butter.
Using a medium to large (at least 4 quart) pot, combine the sugar, corn syrup, and water in this large saucepan and stir to combine. Heat mixture over medium heat until the sugar melts and then increase heat to high to bring the mixture to a full boil. You may occasionally swirl the mixture but do not stir. You may also use a brush to run water down the sides of the pot to wash down any crystals - this will eventually evaporate.
You want to cook the sugar just until it starts to change color and take on more of a caramel color and smell. You'll notice a reduction in the bubbles at this point too. Remove from heat.
To make the caramel, pour the chocolate cream mixture into the sugar, stir to mix, and add your thermometer to the pot. Bring to a boil over high heat and whisk constantly until it reaches 245°F. The moment it reaches temperature, pour it into your prepared pan. Do not scrape out anything that has stuck to the pan as it may have been overcooked.
Allow the caramel to sit for about 10 minutes before sprinkling with salt. If its too hot, the salt will sink in. Start with a small amount and if it sinks, wait a bit longer to add the rest.
Allow to caramel to cool completely at room temperature. Transfer to a cutting board and cut into small pieces. Wrap them individually in wax paper. If you cut the pieces and don't wrap fast enough, they will stick together, so you may want to cut just a few rows at a time.
Store wrapped caramels in an airtight container at room temperature (or you may freeze) until you're ready to share.