Ontario Asparagus and Mushroom Tart - Produce Made Simple

Ingredients

• 2 1/2 Cups Ontario Shiitake Mushrooms, Stemmed and Cut into 1/4 Inch Slices
• 2 Tbsp. Butter
• 1 Sheet Pre-Rolled Frozen Puff Pastry
• Flour for Rolling
• 1 Egg Yolk
• 1/2 lb. Ontario Asparagus, Trimmed and Cut Into 1-Inch Pieces
• 1 Tsp. Chopped Fresh Thyme
• 1 Tsp. Grated Lemon Rind
• 1/2 Tsp. Salt
• 1/2 Tsp. Freshly Ground Black Pepper
• 1/4 Cup Sour Cream
• 1/2 Cup Shredded Gruyere Cheese, Divided