Cook the spaghetti according to the package instructions. Drain and set aside.
In a large pan, heat olive oil over medium heat. Add minced garlic and sauté until fragrant, about 1 minute.
Add the prawns to the pan and cook until they start to turn pink, about 2-3 minutes.
Stir in the harissa paste and cook for another minute, ensuring the prawns are well coated.
Add the cooked spaghetti, salt, and black pepper to the pan. Toss everything together and cook for an additional 2 minutes.
Remove from heat and stir in the lemon juice.
Serve immediately, garnished with chopped parsley.