Place chopped chocolate in a bowl
Heat heavy cream in a saucepan until it begins to simmer
Pour hot cream over the chocolate
Let sit for 1–2 minutes
Stir until smooth and glossy
Add butter and mix until fully combined
Add cocoa powder, water, sugar, and salt to a saucepan
Heat over medium heat while stirring continuously
Bring mixture to a gentle simmer
Cook for about 5 minutes until slightly thickened
Remove from heat and allow to cool
Blend roasted hazelnuts in a food processor until smooth paste forms
Melt chopped chocolate
Add melted chocolate to the hazelnut paste
Add vegetable oil, cocoa powder, and powdered sugar
Blend until smooth and creamy
Add heavy cream, cocoa powder, and sugar to a saucepan
Heat over medium heat while stirring
Add chopped chocolate and butter
Stir continuously until smooth and thick
Remove from heat and let cool slightly
Add cocoa powder, water, and sugar to a saucepan
Heat over medium heat and stir until smooth
Add chopped chocolate
Stir until melted and fully combined
Cook briefly until sauce thickens
Add sugar and water to a saucepan
Heat until sugar dissolves and turns golden caramel
Carefully add heavy cream while stirring
Add chopped chocolate and butter
Stir until smooth and glossy
