Whisk together the sugar, flour, and cocoa.

Whisk in the milk then transfer to a small saucepan.

Cook over medium heat, whisking constantly for 4 to 6 minutes until it begins to boil.

Once boiling, boil for 30 seconds only then remove from heat.

Transfer to a bowl and cover with plastic wrap touching and covering the surface and refrigerate for 1 hour.

Melt the chopped bittersweet chocolate at 30-second intervals, stirring in between, until fully melted, then let cool.

In a stand mixer fitted with a paddle attachment, cream butter then add the pudding mix in small amounts, mixing a couple of times in between additions.

Add the melted chocolate to the stand mixer and beat just until combined.

Add the vanilla and salt and mix on medium speed for 6 to 8 minutes until light and fluffy and light brown in color.