How to Make It
Stir together peas and 1 teaspoon of the salt in a medium saucepan. Add water to cover by a depth of 1 inch. Bring to a boil over high, skimming foam that rises to the top. Reduce heat to medium. Partially cover, and simmer until tender, 15 to 25 minutes. Drain; transfer to a bowl. Set aside.
Preheat oven to 350°F. Cook bacon in a large skillet over medium, stirring occasionally, until crisp, 10 minutes. Transfer to paper towels to drain; reserve drippings in pan. Stir in onion; cook, stirring occasionally, until tender, about 5 minutes. Add spinach in large handfuls. Cook, tossing with tongs to wilt before adding more, until wilted, 3 minutes. Stir mixture into peas in bowl.
Stir together Italian cheese blend, cream cheese, mayonnaise, paprika, garlic powder, cayenne, and remaining 1⁄2 teaspoon salt in a large bowl. Stir in spinach-pea mixture. Transfer to a medium-size ovenproof skillet or 1 1⁄2-quart baking dish, and smooth top. Sprinkle with Parmesan.
Bake in preheated oven until browned, 30 minutes. Let stand 15 minutes. Sprinkle with reserved bacon. Serve warm with baguette slices.