For a smoother guacamole, use a high-speed blender. If you prefer a chunkier texture, mash the avocado by hand and then stir in the remaining ingredients. Roasting the tomatillo and jalapeno before blending will add a smoky depth of flavor. To prevent browning, place the avocado pit in the guacamole until serving or cover the surface with plastic wrap, pressing it directly onto the guacamole. This guacamole is best enjoyed fresh but can be stored in an airtight container in the refrigerator for up to 24 hours. The color may change slightly due to oxidation.