Step 1
Heat broiler. Heat 3 Tbsp. extra-virgin olive oil in a large high-sided ovenproof skillet over medium. Add 2 large shallots, coarsely chopped, 3 garlic cloves, coarsely chopped, and ½ tsp. Diamond Crystal or ¼ tsp. Morton kosher salt. Cook, stirring occasionally, until shallots are translucent, about 4 minutes. Stir in one 14-oz. can artichoke hearts, drained, coarsely chopped, and one 10-oz. package frozen spinach, thawed, drained.
Step 2
Add 8 oz. penne or other short tube pasta, 2 cups whole milk, 2 tsp. Diamond Crystal or 1 tsp. Morton kosher salt, and 1½ cups water to pan and carefully stir to combine. (The pasta should be mostly submerged.) Increase heat to medium-high; bring to a boil. Reduce heat to medium-low; simmer, stirring occasionally and adding up to ½ cup water a little at a time as needed if liquid absorbs too quickly, until most of the liquid is absorbed and pasta is al dente, 16–18 minutes.
Step 3
Remove pasta from heat. Add 4 oz. cream cheese, room temperature, cut into pieces, and stir until incorporated. Add 2 oz. Parmesan, finely grated (about 1 cup), and stir until melted and combined. Add ¼ tsp. freshly ground pepper; taste and season with more salt if needed.
Step 4
Scatter 4 oz. part-skim mozzarella, coarsely grated (about 1¼ cups), evenly over pasta. Broil until cheese is melted, golden brown, and bubbling, about 3 minutes (watch it carefully). Let pasta cool slightly (sauce will thicken as it cools).
Step 5
Serve pasta directly from skillet with hot sauce.
