Ingredient Substitution Guide

1. Step 1

   Halve 5 of the lemons lengthwise. Working over a fine-mesh sieve set in a bowl, scoop out the pulp from each half with a spoon (you can use a knife to help cut around the edges first) and press it through the sieve to extract the juice. Measure out ⅓ cup juice for the possets; save any extra for another use. Set the hollow lemon shells cut-side up on a tray, or nestle them in a muffin tin so they do not tip in the fridge. Zest the remaining lemon.

2. Step 2

   In a medium saucepan, combine the heavy cream, sugar, 1 tablespoon lemon zest and salt. Bring to a gentle boil over medium heat, stirring just until the sugar dissolves. Let it simmer undisturbed for 3 minutes to thicken slightly and concentrate the flavor. (The cream needs to simmer for the full 3 minutes; under-reducing is one of the most common reasons a posset fails to set.)

3. Step 3

   Remove from the heat and pour the cream mixture through a fine-mesh sieve into a heatproof measuring cup or pitcher, leaving the zest behind. Whisk in the lemon juice until fully combined. The mixture will thicken slightly as the acid is incorporated.

4. Step 4

   Pour the posset mixture into the lemon shells while it is still warm — not bubbling hot, but not cooled either. You want it loose enough to pour smoothly; if you wait too long it will start to set. (If that happens, warm it very gently over low heat just to loosen it back up.) Slide the whole tray into the refrigerator and chill uncovered for at least 4 hours, or until fully set.

Tips

• Full-fat heavy cream is the only thing that will set this. Half-and-half, light cream, or anything plant-based will give you a runny pool, not a posset.

• A muffin tin is the easiest way to keep the lemon shells perfectly upright in the fridge — each cup holds one half steady.

• Make-ahead: The possets can be made up to 2 days in advance. Once fully set, cover loosely with plastic wrap.