In a large skillet, heat 2 tablespoons of olive oil over medium heat. Sauté 3 minced garlic cloves until fragrant, about 1 minute. Add in 2 cups of fresh spinach and ½ cup of chopped sun-dried tomatoes, cooking until the spinach wilts, approximately 3-4 minutes. Stir in 4 ounces of cream cheese and ¼ cup of heavy cream until smooth and combined.

Preheat your oven to 375°F (190°C). On a lightly floured surface, roll out one sheet of cold puff pastry into a rectangle approximately 12x16 inches. Place a chicken breast in the center and top it with the creamy filling. Fold the pastry over the chicken, sealing edges tightly; trim excess pastry as needed.

Beat 1 egg in a small bowl for the egg wash. Using a pastry brush, coat the top and sides of the assembled Wellington with the egg wash.

Transfer the wellington to a parchment-lined baking sheet. Bake for 30-35 minutes or until the pastry is puffed and golden brown, reaching an internal temperature of 165°F (75°C) for the chicken.

Remove the wellington from the oven and let it rest for about 10 minutes. Cut into thick slices and serve warm.