Chicken and Mushroom Wellington

Ingredients

• 2 large chicken breasts
• 1 tsp salt, divided
• 1/2 tsp pepper, divided
• 1/4 cup olive oil, divided
• 1/2 lb mixed mushrooms (such as button, cremini, oyster and shiitake), sliced
• 1 small onion, thinly sliced
• 3 cloves garlic, minced
• 1/4 cup dry white wine
• 2 cups baby spinach
• 1/4 cup 35% whipping cream
• 2 tbsp Dijon mustard
• 1 lb 1 pkg. puff pastry, thawed
• 1 egg, lightly beaten