Crisp the bacon in the air fryer: Line the air fryer basket with a perforated liner or a light foil layer (poke holes for airflow). Lay bacon in a single layer. Air fry at 375°F (190°C) for 6–9 minutes, flipping once, until crisp.
Transfer to a paper towel–lined plate. Reserve 1 tablespoon bacon fat if you like.
Sauté aromatics: In a medium pot over medium heat, warm olive oil (or butter/bacon fat). Add chopped onion with a pinch of salt.
Cook 4–5 minutes until translucent and soft. Stir in garlic and cook 30 seconds until fragrant.
Add peas and stock: Tip in frozen peas and 3 cups stock. Bring to a simmer and cook 4–6 minutes until peas are tender and bright green.
Do not overcook or the color will dull.
Blend until smooth: Remove from heat. Add herbs and lemon juice. Use an immersion blender to puree until silky.
For an ultra-smooth finish, blend in batches in a countertop blender, venting the lid carefully.
Adjust texture and season: If the soup is too thick, stir in more stock until you like the consistency. Swirl in cream if using. Season with salt and black pepper.
Add extra lemon to brighten if needed.
Crumble bacon: Chop or crumble the crisp bacon into small pieces.
Serve: Ladle soup into bowls. Top with bacon and any extras like a spoonful of yogurt, croutons, Parmesan, or chives. Serve hot.