Melt the chocolate over a bain-marie or in the microwave and blend or process with the other ingredients.
In a hot pan or pot, add the sugar and water. Let form a caramel and pour over the flan mold. Pour the previous mixture on top and cover with aluminum foil.
Place the stainless steel inner pot inside the Instant Pot®, add 2 cups water, insert the rack, and place the pan on top.
Close and lock the Instant Pot® lid. Make sure the steam release handle is turned to Sealing. Press Pressure Cook, pressure level High, and set time to 30 Minutes.
When done cooking, let the steam release naturally. Once all the pressure has released, press Cancel. Let cool completely and unmold.
Garnish with nuts and grated or shredded chocolate and refrigerate for at least 2 hours before serving.