Step 1 – Heat the milk and cream
In a medium saucepan, combine the milk and heavy cream. Warm over medium heat until steaming but not boiling. Remove from heat.

Step 2 – Whisk the eggs
In a separate bowl, whisk together the egg yolks, whole egg, sugar, cornstarch, and salt until smooth and pale.

Step 3 – Temper the eggs
Slowly pour about ½ cup of the hot milk mixture into the egg mixture, whisking constantly to avoid curdling. Then whisk in the remaining milk mixture.

Step 4 – Return to saucepan and cook
Pour everything back into the saucepan. Cook over medium heat, whisking constantly, until the custard thickens and coats the back of a spoon—about 5 to 7 minutes.

Step 5 – Add lemon and strain
Remove from heat. Stir in the lemon zest, lemon juice, and vanilla extract if using. Strain through a fine mesh sieve into a clean bowl to remove zest and ensure smoothness.

Step 6 – Chill and serve
Pour into ramekins or jars. Cover with plastic wrap (pressed directly onto the surface) and refrigerate for at least 2 hours or until fully set. Garnish with whipped cream, berries, or zest before serving.