Whisk dry bases. In a bowl, whisk the brown sugar, granulated sugar, cornstarch, and salt. This helps avoid lumps and gives you that smooth mouthfeel.

Milk it up. In a heavy saucepan, combine the milk and cream. Heat gently until it’s just about to simmer, then whisk in the sugar mixture.

Thicken with science. Bring to a simmer, then whisk constantly for 1–2 minutes as the cornstarch activates. The mixture will thicken and look a little shiny.

Buttery bliss. Remove from heat, whisk in the butter chunks until fully melted and glossy. Stir in vanilla and taste—adjust sweetness if you’d like.

Chill out. Return to a clean pot if needed and cook gently for another minute to ensure everything’s set. Pour into cups or a serving bowl and chill in the fridge for at least 2 hours.