Rinse the stalks of asparagus then snap of the tough ends at the bottom where a break naturally occurs. (Literally grab the lower end of the stalk and it will snap right off.)
Line a large rimmed baking sheet with a Silpat liner or foil. Spread the asparagus out on the pan and drizzle 2 tablespoons of the olive oil over the stalks and toss to coat evenly. Sprinkle with ½ teaspoon of the kosher salt and ¼ teaspoon of the pepper.
Roast in a 400-degree oven for 18 to 20 minutes, or until tender when pierced with the tip of a sharp knife.
While the asparagus is roasting melt butter with the remaining 1 tablespoon of olive oil in a shallow stockpot or large saucepan over medium heat. Sauté the onion until tender and translucent, about 8 to 10 minutes.
When the asparagus is cool enough to handle cut it into smaller pieces, reserving some of the tips for garnish.
Combine the asparagus, chicken stock, concentrated chicken base, and cream with the sautéed onions. Purée until the soup until smooth using a blender or immersion blender. Season with the remaining kosher salt and pepper as needed.
Return to the stockpot cook over medium heat until warmed through, or if using a Vitamix use the soup setting to heat. Garnish with reserved roasted asparagus tips.