Begin by slicing ripe avocados in half and removing the pits. Scoop the flesh into a blender along with freshly squeezed lime juice, your choice of fresh herbs, and sour cream or Greek yogurt. Blend the mixture on high speed until it's velvety smooth and creamy, which should take about 1-2 minutes. Stop blending and scrape down the sides as needed for an even texture.

Taste the avocado mousse and decide if it needs more lime juice or a pinch of salt to enhance the flavors. Blend again for a few seconds to incorporate any adjustments.

Transfer the avocado mousse into an airtight container. To prevent browning, place a sheet of plastic wrap directly on the surface of the mousse before sealing the container. Chill it in the refrigerator for at least 1 hour.

After the mousse has chilled, remove it from the fridge and stir gently to restore its creamy texture. Spoon the avocado mousse into your preferred serving dishes.

Carefully layer slices of smoked salmon over the avocado mousse in each serving dish. Add extra herbs on top for a pop of color and additional flavor.

Present your assembled mousse and smoked salmon to your guests as a stunning appetizer, and serve alongside artisan crackers or slices of baguette.