The almond has been a treasured ingredient as long as recorded history. It played an important role in early Arab and medieval cooking, and long before chefs learned to use roux or eggs to thicken their soups and sauces, they used bread and nuts. Traditional almond soups, rich with garlic, are still common in Spain, but this creamy version has a more 20th-century American profile. It’s delicious and unexpected.
In a 4- to 5-quart heavy-bottomed pot over low heat, toast the nuts until nicely browned, 5 to 7 minutes. Transfer to a bowl. Return the pot to medium heat, melt the butter, and add shallot. Cook until translucent, about 2 minutes. Add the flour and stir until glossy, about 3 minutes. Add the toasted almonds, broth, lemon juice, sugar, salt, and pepper. Reduce heat to medium-low and cook, stirring occasionally, for 15 minutes.
In a blender, purée the soup in batches until smooth (this may take a few minutes), then return it to the stove and add the cream, tarragon, and, if desired, almond extract. Serve garnished with additional tarragon.