Guacamole with lemon

4 -6 Hass avocadoes , very large and ripe, peeled, coarsely chopped (count depends on size) 3/4 cup sweet onion , diced (use Walla-Walla, Vidalia, or red) 2/3[...]

1 tablespoon oil 1 teaspoon black mustard seeds 1/2 teaspoon cumin seed 3 large avocados 1 tablespoon lemon juice 1 garlic clove , minced 1 serrano chili ,[...]