Wash the fresh cilantro bunch and cut off any long stems.
Place the washed cilantro, 3 cloves of garlic, 1/4 cup of lime juice, 1 fresh jalapeno, (with the stem and seeds cut out) and 1/2 teaspoon of salt in a food processor.
Blend until all ingredients are chopped fine, then slowly add 1/3 cup of oil while the food processor is running. Scrape the edges if needed and blend until creamy.
Notes
Adding the oil slowly at the end helps to emulsify the sauce and make it creamier than if you just added it all together.