**Making the Crème Patisserie:**

1. In a saucepan, heat milk, cream, and vanilla until simmering.
2. In a bowl, whisk together egg yolks, sugar, and salt.
3. Slowly pour a third of the hot cream mixture into the egg mixture while whisking.
4. Return the mixture to the saucepan and cook on low heat until it thickens into custard.
5. Stir in butter, strain the custard, cover, and refrigerate for 1-2 hours.

**Preparing the Donut Rolls:**

1. Preheat the oven to 350°F and line a cookie sheet with parchment paper.
2. Separate the Hawaiian rolls and coat each in melted butter.
3. Bake for about 8 minutes until golden.
4. Coat the rolls in sugar and let them cool.

**Filling the Donuts:**

1. Transfer the cooled custard to a piping bag.
2. Puncture each roll and fill with custard.
3. Place rolls sideways and prepare for caramel.

**Caramel & Coating:**

1. In a saucepan, combine sugar and water and boil until golden.
2. Dip the top of each donut roll in the hot caramel.
3. Wait 10 minutes for the caramel to harden.