Pour the milk into a 2-quart saucepan. Add the vanilla bean pod and scraped seeds. Let the milk and vanilla sit for 5 minutes off the heat to start infusing.

Place the saucepan over medium heat and warm the milk until it just begins to steam and small bubbles form at the edges, about 4 to 5 minutes. Do not boil. Remove the vanilla pod.

While the milk heats, whisk together the egg yolks, granulated sugar, cornstarch, and a pinch of salt in a mixing bowl until the mixture is pale yellow and smooth, about 1 minute.

Slowly ladle about one third of the hot milk into the egg yolk mixture, whisking constantly to temper the eggs. Pour in a thin stream to avoid scrambling.

Pour the tempered egg mixture back into the saucepan with the remaining hot milk, whisking as you pour.

Return the saucepan to medium heat. Add the maple syrup and whisk constantly for 5 to 7 minutes until the mixture thickens enough to coat the back of a wooden spoon and hold a clean line when you draw your finger through it.

Remove the pan from the heat. Add the cold butter pieces and whisk until fully melted and the pudding is glossy and smooth.

Pour the pudding through a fine-mesh sieve into a clean bowl or directly into 4 ramekins, dividing evenly.

Press a sheet of plastic wrap directly onto the surface of each pudding to prevent a skin from forming. Rest for 10 minutes at room temperature, then refrigerate for at least 2 hours if serving chilled, or serve warm immediately.