For the French dressing: Plop the ketchup, yogurt, vinegar, mustard, sugar, paprika, onion and salt to taste into a high-speed blender. Puree until smooth. Use immediately or transfer to an airtight container and store in the refrigerator for up to 2 weeks.
For the pea and bacon salad: Put the bacon in a large cold skillet and cook over medium heat until crisp, 4 to 5 minutes. Drain on a paper towel-lined plate, and set aside.
Add the peas to the bacon fat, then sprinkle lightly with salt and pepper and cook over medium heat until they get a slight color, 2 to 3 minutes. Remove from the heat and set aside.
Build the salad. Onto a bed of butter lettuce leaves, scatter the peas and herbs. Crumble and add the bacon. Finish with a grating of Parmesan and a drizzle of dressing. Serve with more dressing on the side.