Place the chocolate in a large mixing bowl. Set aside.

In a heat-proof bowl, add the egg yolks, sugar and salt. Whip until the mixture turns into a pale yellow color and fluffy. Set aside.

Into a saucepan, add the milk, heavy cream, and instant coffee. Heat the mixture until it starts simmering.

Slowly, pour the hot milk with cream into the bowl with eggs and sugar while whisking continuously to prevent egg yolks from curdling.

Pour the mixture back into the saucepan and cook it over low heat stirring continuously until the mixture reaches 179F (82C). It will take approximately 10 minutes.

When done, pour the custard through a fine-mesh strainer into the bowl with the chocolate.

Mix until all chocolate has melted and the mixture is glossy and has a smooth and homogenous consistency. Additionally, you can blend the mixture using an immersion blender to make sure that the mixture has emulsified.

Cover with plastic wrap so it touches the entire surface of the chocolate cremeux.

Allow to cool down to room temperature or slightly chill in the fridge before pouring into your tart shells. Or, refrigerate for 6 hours or overnight to use it as a cake filling, or pipe it on top of your desserts as a decoration.