Ingredients

• 1 medium leek, white and light-green parts only, cut crosswise into 1/3" rounds
• 5 tablespoons (or more) olive oil, divided
• 1 pound sweet Italian sausage (about 4 links), cut into 1/4" coins
• 2 garlic cloves, thinly sliced
• 3 tablespoons all-purpose flour
• 2 cups leftover chicken stock or low-sodium chicken broth
• 2 medium carrots (about 5 1/2 ounces), peeled, cut into 1/4" coins
• 4 small new potatoes (about 5 ounces), cut into 1/2" cubes
• 6 ounces frozen peas, thawed
• 1 tablespoon chopped dill
• 1/4 cup fresh lemon juice, divided
• 1 1/4 teaspoons kosher salt, divided
• 3/4 teaspoon freshly ground black pepper, divided
• 1 sheet frozen puff pastry, such as Dufour or Pepperidge Farm, thawed
• 1 large egg (optional)
• 5 cups baby spinach (about 4 ounces)
• 4 cups baby arugula (about 3 ounces)
• 3 radishes, thinly sliced
• 1/4 cup cilantro, coarsely chopped
• 1/4 cup parsley, coarsely chopped
• 1/4 cup sliced almonds

Instructions

1. Place rack in upper third of oven; preheat to 425°F. If you see or feel dirt in leeks, rinse well, separating layers, then pat dry; otherwise, leave rounds intact.
2. Heat 1 Tbsp. oil in a 10" cast-iron or other deep, heavy, ovenproof skillet over medium-high. Cook sausage, stirring occasionally, until browned, 5–7 minutes. Add garlic and cook until golden brown, about 2 minutes more. Using a slotted spoon, transfer sausage and garlic to a plate, reserving about 2 Tbsp. oil in pan.
3. Return pan to low heat and add flour, 1 Tbsp. at a time, stirring to combine. Cook, stirring constantly, until mixture starts to smell toasty and is the color of peanut butter, about 5 minutes.
4. Stir in stock 1/4-cupful at a time. Bring to a boil, then reduce heat to medium-low. Add carrots, potatoes, and leek and simmer until carrots and potatoes are just softened and liquid is reduced by half, 10–12 minutes. Add reserved sausage and garlic, peas, dill, 2 Tbsp. lemon juice, 3/4 tsp. salt, and 1/2 tsp. pepper and stir to combine.
5. Remove from heat. Place pastry over skillet, tucking corners gently into sides; it won't completely cover pan. Whisk egg with 1 Tbsp. water (if not using, substitute 1 Tbsp. oil) in a small bowl and brush top of pastry. Cut four 1" slits in pastry to vent.
6. Bake pot pie until pastry is beginning to brown and underside is cooked, 23–25 minutes. Let cool 10 minutes before serving.
7. Meanwhile, whisk remaining 4 Tbsp. oil, 2 Tbsp. lemon juice, 1/2 tsp. salt, and 1/4 tsp. pepper in a large bowl. Add spinach, arugula, radishes, cilantro, parsley, and almonds and toss to combine.
8. Divide pot pie among plates and serve salad alongside.