For the Mushrooms:
Heat the sunflower oil in a large skillet over medium-high heat.
Add the mushrooms and sauté for 3-4 minutes until they start to brown.
Add the julienned onion and garlic and sauté for another 2-3 minutes.
Add the butter, salt, pepper, smoked paprika, and Italian herbs. Stir to combine.
Sprinkle the chopped parsley over the mushrooms and stir to combine.
For the Garlic Sauce:
In a small bowl, combine the Greek yogurt, mayonnaise, minced garlic, salt, pepper, and chili flakes (if using).
Stir in the agave syrup, chopped parsley, and chopped chives.
Serve the mushrooms warm, with the garlic sauce on the side.
