Add the minced garlic, the egg yolk, the mustard, and the black pepper to a small bowl. Give everything a little stir, to incorporate.
Slowly incorporate the oil in a very thin stream, while constantly beating with a fork or mini whisk. (Add a little oil at a time, waiting until the oil has 'disappeared', before adding more.) The whole process should take about 5 minutes--the mayonnaise will have risen in the bowl and turned a paler yellow. You should also be able to tip the bowl over without the mayonnaise falling out.
Let the mayonnaise rest in the fridge, covered, for at least one hour before use. (This can also be made a night ahead.)
Wash and thinly slice the scallions. Add them to a medium-sized bowl.
About the lobster: my fishmonger happens to sell freshly-cooked, whole lobsters. You can also buy live lobsters, and cook them yourself.
Chop your lobster into bite-sized pieces, and then add them to the medium bowl. Also add: the lemon juice, the cayenne, and the mayonnaise. Gently toss all ingredients together, to incorporate. Serve the salad slightly chilled.
Cristina is a writer, cook, and day job real estate developer. She studied literature, holds an MFA in Fiction Writing, and completed the Basic Cuisine course at Le Cordon Bleu in Paris. She lives in Jersey City with her husband--a Frenchman she met in Spain--and their sweet black cat, Minou. Follow her writings, recipes, publications and photography at theroamingkitchen.com.