Cook the pasta in plenty of boiling salted water for about 15 minutes. In the meantime peel onion and cut into fine strips. Peel garlic and chop finely. Fry bacon in a pan without fat until crispy.
Take out and drain on kitchen paper. Add olive oil to the pan and heat. Fry the onion strips and garlic in it. Deglaze with vegetable stock. Add mascarpone and stir until smooth.
Add the peas and bring to the boil. Let simmer for about 5 minutes. Rip bacon into strips and add to the sauce. Season with pepper and lemon juice. Drain noodles and arrange on plates with the sauce.
Garnish with basil leaves.