Heat the olive oil in a large sauté pan over medium heat. Season chicken with salt and pepper and add them to the pan in a single layer.
Sauté the chicken on both sides until golden brown, about 2 minutes per side. Transfer the chicken to a platter and keep warm.
Meanwhile, place the asparagus in a microwave safe bowl with a splash of water and cover loosely with plastic wrap. Microwave the asparagus on high until it is just tender, about 2 to 3 minutes. Drain and set aside.
Lower the heat and add the onions. Cook until the onions are soft and translucent, about 5 minutes. Add garlic and cook for 1 minute more.
Add wine to the pan, turn heat to medium and reduce the wine until it is almost completely evaporated.
Add chicken broth and reduce it by half. Whisk in the mustard, sour cream, and tarragon and stir until the sauce is smooth and creamy.
Add the chicken and asparagus to the sauce to heat them for a minute or two.
Transfer the chicken and asparagus to a platter. Sprinkle with a little tarragon if using fresh.
There are 272 calories in 1 serving of Chicken and Asparagus with Cream Dijon Sauce.