Roast the garlic head by cutting a thin slice off the very top of the head to expose the tops of all the cloves. Set the head in a shallow baking dish, and drizzle 2T olive oil over the head and season with salt and pepper.
Cover w/ foil.
Bake in a 300 degree oven for 1-1/2 hours till garlic is very soft.Set aside.
When cool squeeze the pulp out of the garlic into a blender and add egg yolks, garlic, lemon juic, water, salt, and cayenne.
Puree till smooth.
With motor running add the reserved oil from roasted garlic plus the additional 1-1/2 c oil in a slow steady stream and continue processing till emulsified.