Warm the dairy: In a small pot, heat the milk and cream over low until just steaming. Do not boil. Keep warm on the lowest heat.

Make the butterscotch base: In a medium saucepan, melt the butter over medium heat. Stir in the dark brown sugar and salt. Cook, stirring, for 2–3 minutes until the mixture looks thick and glossy and smells caramel-like.

Whisk the yolks and cornstarch: In a bowl, whisk egg yolks with cornstarch until smooth. Add a splash of the warm milk mixture to loosen if needed.

Temper the yolks: Slowly pour about 1 cup of the warm milk-cream into the yolk mixture while whisking constantly. This prevents curdling.

Combine and cook: Pour the tempered yolk mixture back into the saucepan with the remaining warm dairy and the butterscotch base. Whisk well to combine.

Thicken the dessert: Cook over medium heat, whisking constantly, until the mixture bubbles and thickens, 3–5 minutes. Once it starts to bubble, keep whisking for 1 minute to cook out the cornstarch flavor.

Finish with vanilla: Remove from heat and whisk in the vanilla. Taste and add a pinch more salt if you prefer a salted-butterscotch vibe.

Strain for silkiness: For the smoothest texture, pour the mixture through a fine-mesh sieve into a bowl or measuring jug.

Portion and chill: Divide into ramekins or glasses. Press plastic wrap directly on the surface to prevent skin if you don’t like it. Chill at least 2 hours for a firm, creamy set. Or serve warm after 10 minutes of resting for a softer, custardy texture.

Garnish and serve: Top with a dollop of whipped cream, a few flakes of sea salt, or crunchy toffee bits for contrast.