Easy Spinach and Artichoke Pasta Bake (with Frozen Spinach)

Ingredients

• 1 pound dried penne pasta
• 1 tbsp olive oil
• 1 shallot, diced
• 3 garlic cloves, minced
• 10 oz fresh baby spinach, or frozen chopped spinach, defrosted and drained
• 1 (14-ounce) can artichoke hearts, drained and roughly chopped
• 1/2 tsp kosher salt
• 1/4 tsp red-pepper flakes, optional
• black pepper
• 1 cup milk
• 8 oz cream cheese
• 2 oz (about 1/2 cup) grated Parmesan
• juice from 1/2 lemon
• 2 oz (about 1/2 cup) shredded mozzarella cheese