Melt the chocolate with the butter, soluble coffee and salt, which can be done in two ways. The first is in a double boiler, placing a medium pot with plenty of water over medium heat. Then, add these ingredients to a large heat-resistant bowl and place it on top of the pot with water (without touching the water) so that they melt with the steam.The second is in the microwave, adding these ingredients to a large microwave-safe bowl and then melting them for 30-second intervals, i.e., put the bowl in the microwave for 30 seconds and take it out after this time to mix a little with a fork. Repeat the process until both the chocolate and the butter are completely melted.
Separately, in a large bowl add the very cold whipping cream with the vanilla extract and beat with an electric mixer or a hand whisk for 3-4 minutes until stiff peaks form and the cream is fluffy. It is important to beat only to this point and not to overbeat.
Carefully add the chocolate mixture (which should already be cold) to the bowl with the whipped cream and mix with a rubber spatula until both mixtures are integrated and there are no lumps. At the end you will have a very smooth and creamy mixture.
Cover the mixing bowl with plastic wrap and refrigerate for at least 2 hours so that the mixture hardens a little and the truffles can be formed.
Once the mixture is firmer, form the truffles. To do this, using your hands form small balls the size of 2 teaspoons each and place them on a tray with baking paper so they do not stick. Refrigerate the truffles for 15 minutes.
When the truffles are firmer, dip them in the cocoa powder to coat them completely. If desired, they can also be decorated with shredded coconut, chopped peanuts or colored sprinkles.