Wash Lemons: Rinse under running water and optionally soak in a baking soda solution to remove pesticides.
2 lemons
Zest and Juice: Use a microplane or zester to remove the zest, then juice the lemons.
Infuse Milk: Heat the milk with lemon zest until bubbles form at the edges, then turn off the heat and let it steep for 20-30 minutes.
1 3/4 cups milk
Mix Yolks: While the milk heats, whisk yolks, cornstarch, and 2 tablespoons of the milk mixture (while it's still lukewarm) in a bowl.
4 egg yolks, 4 tablespoons cornstarch
Boil Milk: Add the vanilla extract and sugar to the infused milk and bring it back to a boil, then remove from heat.
1 teaspoon vanilla extract, 7 tablespoons sugar
Temper Yolks: Slowly add hot milk to the egg mixture, whisking constantly to avoid curdling.
Cook Cream: Return the mixture to the pot and cook on low heat, stirring constantly until thickened and bubbly.
Finish Cream: Remove from heat, whisk for an additional minute.
Add Butter and Lemon Juice: Stir in butter until melted, then add the lemon juice.
2 tbsp unsalted butter
Taste and Adjust: Test the flavor and adjust sweetness or tanginess as needed.
Strain (Optional): Strain to remove zest or any lumps for a smoother texture.
Cool and Chill: Cover with plastic wrap touching the surface and cool at room temperature for 30 minutes, then refrigerate.
Prepare for Use: Whisk chilled pastry cream until smooth before using.