• Preheat the oven to 300°F/ 150°C. Place the small jars into the baking dish.

Potted cream mixture:

• Whisk the heavy cream, salt, and muscovado sugar in a saucepan. Heat on medium heat while stirring until the sugar dissolves and the cream just begins to simmer. Set aside.

  2 cups heavy cream + ½ cup muscovado sugar ¼ teaspoon fine sea salt
• Caramelize sugar: Place the water and the granulated sugar in a medium saucepan. Heat over medium heat while stirring to dissolve the sugar. When the sugar is dissolved and the mixture starts to boil, continue to cook, occasionally stirring, until the water has reduced and the mixture bubbles and turns a medium amber color. This will take about 5 minutes.

  ⅓ cup water + ⅓ cup granulated sugar
• Combine: Remove from the heat and slowly whisk in the heavy cream-muscovado mixture. Stir until combined. If the caramel doesn't completely dissolve, return the pan to low heat for about 1 minute and stir continuously until the caramel is dissolved.
• Mix the egg yolks, vanilla extract, rum, and butterscotch flavor.

  6 large egg yolks + 1 teaspoon pure vanilla extract + 1 teaspoon butterscotch flavor + a few drops of rum flavor
• Very slowly and in a steady stream pour the egg yolks into the caramel mixture while whisking all the time.
• Strain the mixture through a fine-mesh sieve and skim off any foam with the help of a spoon.
• Divide the mixture equally into the jars.

Bake potted cream:

• Pour hot water (from a kettle) into the baking dish holding the jars, the water should come halfway up the sides of the jars.
• Bake, uncovered, for about 35 to 40 minutes. When ready, the cream should be set but still jiggle slightly in the middle. Remove from the oven and let cool completely in the baking dish with the water; they will continue to set as they cool.
• Serve with freshly whipped cream. The custards can be covered and refrigerated until the next day. Take out of the fridge one hour before serving and decorate with whipped cream only before serving.

  1 cup heavy cream