In a heavy-bottomed saucepan, warm the milk over medium heat until it begins to steam but does not boil. Remove from heat.

In a separate bowl, whisk together the egg yolks, sugar, cornstarch, and salt until the mixture is pale and slightly thickened.

Slowly pour 1/2 cup of the warm milk into the egg mixture while whisking constantly to prevent scrambling and temper the eggs.

Gradually whisk in the remaining warm milk, then pour the entire mixture back into the saucepan.

Cook over low to medium heat, stirring constantly, until the custard thickens and coats the back of a spoon, taking care not to let it boil.

Remove from heat and stir in the butter and vanilla extract until the custard is smooth and glossy.

Strain the custard through a fine-mesh sieve into a clean bowl to ensure a perfectly smooth texture.

Press plastic wrap directly onto the surface of the custard to prevent a skin from forming, let it cool at room temperature, then refrigerate until chilled.

Serve chilled in bowls or cups. You can warm a small portion gently for a cozy snack.

Top with fresh berries, a dusting of cinnamon, or a drizzle of caramel.

For a simple plated dessert, spoon over sliced fruit or use as a filling for tart shells.

Cover the custard surface with plastic wrap to stop a skin from forming. Refrigerate in an airtight container for up to 3 days.

Do not freeze; the texture will change. If the custard thickens too much, stir in a little warm milk to loosen before serving.