1. Preparing the Mushrooms:

• Preheat your oven to 400°F (200°C).
• Roughly chop the mushrooms and place them in an oven-safe container.
• Drizzle the olive oil and add ¼ cup of chopped chives to the mushrooms. Toss to coat evenly.

2. Roasting the Mushrooms:

• Place the mushroom mixture in the preheated oven.
• Roast for 20 minutes, or until the mushrooms are tender and slightly browned.

3. Making the Roux:

• While the mushrooms are roasting, melt the butter in a large stockpot over medium heat.
• Stir in the flour to form a roux, mixing them together until smooth.
• Cook this mixture for about 5 minutes, stirring frequently. The roux should turn a light golden brown but not burn.

4. Adding Ingredients to the Roux:

• Season the roux with cracked black pepper and salt.
• Carefully add the roasted mushroom mixture from the oven into the stockpot.
• Stir to combine the ingredients with the roux.

5. Adding Beef Stock:

• Gradually pour in the beef stock while continuously stirring to ensure the mixture blends smoothly.
• Cook over medium heat for about 10 minutes. The soup should start to thicken.

6. Adding Heavy Cream:

• Reduce the heat to low and stir in the heavy cream until fully combined.
• Allow the soup to simmer gently for an additional 15 minutes, stirring occasionally. Avoid boiling to prevent the cream from separating.

7. Final Touches and Serving:

• After simmering, check the seasoning and adjust if necessary.
• Serve the soup hot.
• Garnish each bowl with a sprinkle of the remaining chopped chives and a drizzle of truffle oil for a luxurious finish.