Start by making the pasta dough. In a food processor, combine the egg and flour until it becomes breadcrumb-like in texture. Wrap in cling film and place in the fridge until needed.
Place the mint and oil in a blender. Blend until smooth, then pass through a fine sieve or muslin cloth. Reserve the oil.
Bring a pan of salted water to the boil and cook the frozen peas and then the asparagus. Reserve 4 asparagus tips for later and blend the rest with the ricotta, nutmeg and 1 tbsp peas. Taste and season with salt and pepper if needed. Place in a piping bag in the fridge until later.
Blend the rest of the peas with the veg stock until smooth. Season to taste.
Roll out the dough to the finest setting on a pasta machine and cut discs around 8cm in diameter. Pipe a ball of the asparagus and ricotta mix onto the centre of each. Wet a finger and run a line of water around the ricotta mix. Fold the pasta dough over to create a pocket of filling, then pinch the sides together to create your tortellini. Repeat until you have used all your filling or dough. Reserve under a cloth to prevent drying out or freeze if using on another day.
Reheat the pea puree on the stove. Bring a large saucepan of water to the boil and salt generously. Drop the pasta in the water and cook for 4 mins (5 if frozen). Ladle the pea puree into a bowl and place the tortellini in the puree. Garnish with 2 asparagus tips and a squeeze of mint oil.