Remove skin and bones from fish and flake flesh with a fork. 

In a deep bowl, mash egg yolks with milk until they form a smooth paste. Add sugar, salt, and 1 tablespoon of lime juice.

 Beat in vegetable oil, a teaspoon or so at a time. Add olive oil in the same gradual manner. 

Chop egg whites finely and add to the bowl, along with fish. Combine thoroughly but gently. 

Just before serving, cut avocados in half, remove pits, and fill cavities with fish mixture. 

Garnish with pepper or pimento, and pass around the remaining lime juice to sprinkle on individual servings.