Place the finely chopped dark chocolate in a medium heatproof bowl. Set aside.

In a small saucepan, heat the heavy cream over medium heat until it just begins to simmer around the edges. Do not let it boil. Remove from heat and stir in the instant espresso powder and salt until fully dissolved.

Pour the hot espresso cream over the chopped chocolate. Let the mixture sit undisturbed for 5 minutes to allow the chocolate to melt. Add the softened butter and vanilla extract.

Using a rubber spatula, slowly and gently stir the mixture, starting from the center and working your way out, until the ganache is completely smooth, glossy, and emulsified.

Cover the bowl with plastic wrap, pressing it directly onto the surface of the ganache to prevent a skin from forming. Refrigerate for at least 2 hours, or overnight, until firm enough to scoop and roll.

Line a baking sheet with parchment paper. Use a small cookie scoop (about 1 tablespoon) to create even portions of the chilled ganache. Flatten each portion slightly in your palm, place one soft caramel candy in the middle, and carefully roll the ganache around it to form a complete ball.

Place the cocoa powder in a shallow bowl. Roll each completed truffle in the cocoa powder until it is evenly and generously coated. Place the finished truffles on the prepared baking sheet.

For the best texture, allow the truffles to sit at room temperature for about 20 minutes before serving. Store in an airtight container in the refrigerator.