Preheat oven to 375° (190C). Butter the inside of your soufflé molds ( I used 3 1/2 Inch- 9 cm Ramekins). Dust the molds with granulated sugar, then pour out the excess.
Place milk and cream in a small saucepan and stir over medium heat until it boils. Remove from heat, add chocolate. Let sit for 1 minute then stir until well combined and all of the chocolate has melted.
Add the cocoa powder and water, and whisk until very hot over a bain-marie (double boiler).
Remove from the heat and set aside to cool for a few minutes.
Meanwhile, whip the egg whites with salt until foamy. Gradually add sugar and beat until stiff peaks form.
Add egg yolks to chocolate mixture and whisk in to combine.
Using a rubber spatula gently mix one-third of the egg whites into the chocolate mixture. Then fold the chocolate mixture into the remaining whites. Spoon batter into prepared molds.
Bake until the soufflé has risen to about 1 1/2 inch above the dish, for about 13-15 minutes.
Meanwhile whip the cream with powdered sugar if used for serving.
Remove from the oven, dust the top with powdered sugar, and add a spoon of whipped cream. Serve immediately as the souffle will begin to deflate after about 2 minutes.