Add the mayonnaise, sour cream, and garlic to the bowl of a food processor fitted with an S-blade and pulse until the garlic is minced. This will take about 30 seconds.
Add the lemon, parsley, tarragon, and chives. Pulse for about 45 seconds or until the herbs are finely chopped and the dressing is your desired consistency.
Season with salt and pepper.
Refrigerate in an airtight container for up to 3 days.
For the Salad:
Add all of the salad ingredients to a large bowl.
Drizzle the dressing over the top and toss to serve.
Sprinkle the almonds over the top and serve immediately. The avocado will brown if it sits, and the almonds will soften, so serve immediately.
Notes
You can use whatever mix of lettuce you’d like. I like the crispness of romaine hearts and the flavor of the mixed greens.