Mushroom Wellington

Ingredients (16)

• 1/2 cup pearled farro
• 1 cup milk
• 1/3 cup fresh tarragon leaves, divided
• 1 cup 1/2-inch dice butternut squash
• 1 cup 1/2-inch dice sweet potato
• 5 tablespoons olive oil, divided
• Kosher salt, to taste
• Freshly ground black pepper, to taste
• 8 ounces large portobello mushrooms
• 4 tablespoons (2 ounces) unsalted butter, divided, more for the baking pan
• 1 medium shallot, diced
• 1 ounce baby kale, coarsely chopped
• 1 tablespoon all-purpose flour
• 24 ounces puff pastry;  two sheets measuring 14 x 9-inches, defrosted according to package directions.
• 1 large egg, lightly beaten
• 1 cup heavy cream