Have a fine-mesh sieve ready over a medium bowl. Whisk egg yolks in a separate bowl. In another small bowl, whisk sugar, cornstarch, and salt.

In a heavy saucepan, heat milk and cream until steaming (small bubbles at edges). Remove from heat. Whisk in nutmeg, cinnamon, allspice, and cloves. Cover and steep for 10 minutes.

Return saucepan to medium-low heat to re-warm. Whisk the sugar-cornstarch mix into the egg yolks to form a thick paste.

Slowly whisk about 1 cup of the hot dairy into the egg yolk mixture to temper. Then, pour this mixture back into the saucepan, whisking constantly.

Switch to a spatula. Cook over medium-low heat, stirring constantly, until thickened and bubbling with large, slow bubbles. Cook for 1 full minute while stirring.

Remove from heat. Stir in vanilla, butter, and spirits (if using) until butter melts. Immediately pour through the sieve into the bowl.

Press plastic wrap directly onto the pudding's surface. Refrigerate for at least 4 hours, or overnight, until completely set.

Before serving, whisk briefly to loosen. Spoon into dishes and top with whipped cream, nutmeg, or crushed cookies.