Place the egg yolks in a bowl. Finely crush the peppercorns and mustard seeds in a mortar, then add to the yolks. Using a hand mixer, beat until creamy. Add the oil a drop at a time until incorporated. Increase to a thin stream as the oil becomes easier to incorporate, stirring strongly, until a creamy mayonnaise forms.
Peel the garlic, and mash finely with 1-2 tablespoons in a blender. Add to the mayonnaise, and season to taste with salt.
This can be done 1 hour ahead of time. Serve in bowls.