A trick to make mayonnaise is to drape a dishtowel over a small saucepan and set a metal bowl on it. This holds the bowl containing the mayonnaise in place and gives you the height you need for easy whisking. You can also use a hand mixer for this step, in which case, you will likely need to loosen up the mixture periodically with a few drops of warm water.
1 large pasteurized egg yolk, at room temperature
2 teaspoons fresh lemon juice
1 teaspoon Dijon mustard
1/4 teaspoon table salt
3/4 cup vegetable or canola oil
3 teaspoons prepared horseradish
2 teaspoons Creole mustard (such as Zatarain's) or other whole-grain mustard
Pinch of cayenne pepper
How to Make It
Whisk together egg yolk, lemon juice, Dijon mustard, and salt in a medium bowl until smooth. Slowly dribble in oil, whisking constantly. When mixture starts to thicken, add oil in a thin stream until completely incorporated. (If mayonnaise gets too thick, add 1 teaspoon water.)
Add horseradish, Creole mustard, and cayenne, and whisk until incorporated. Cover with plastic wrap, and chill until ready to use.