In a small bowl, whisk together cream, espresso, vanilla extract, and coffee extract; set aside. In a medium heavy-bottomed saucepan, combine sugar and water. Bring mixture to a boil over medium heat, whisking constantly. Once mixture begins to boil, about 2 to 3 minutes, reduce heat to medium-low. Cook, without whisking, until mixture registers 350° on a candy thermometer, about 10 to 15 minutes.
Remove mixture from heat, and whisk in butter and salt until butter is melted.* Add cream mixture to sugar mixture, and whisk until smooth. Let cool to room temperature for at least 1 hour. Whisk before using.
Notes
*Use caution as mixture is very hot, and the steam can cause burns.
Recipe by Victoria at https://victoriamag.com/chocolate-salted-coffee-caramel-tart-recipe/