Oven temperature: 220°C Gas mark 7.
Thaw the peas, peel and finely chop the onion.
Wash and drain the green asparagus, cut the tips off the spears and reserve.
Heat the butter in a pan and sweat the onion until soft.
Add the stock, herbs and seasonings and bring to the boil.
Reserve 1 tbsp peas and add the rest of the peas, the asparagus stalks (without the tips) and the diced potato to the onion stock.
Cook for about 5 minutes.
Drain and roughly mash with a potato masher.
Mix in the crème fraîche and season to taste with salt, pepper and lemon juice.
Place the baguette slices on a baking tray and toast in a hot oven for about 3-5 minutes.
Meanwhile quickly sauté the asparagus tips and reserved peas in a little olive oil.
To serve, spread the toasted bread while still hot with the pea and asparagus puree.
Top with the fried asparagus tips and peas and scatter the crostini with Parmesan shavings.
Drizzle with olive oil and sprinkle with pepper if you wish.
Arrange attractively on a platter with the rocket leaves.