Fill a pan with a little over 1 litre of water. Cut the lemon through the middle. Wash the celery stalk and cut it through the middle. Add these ingredients with one teaspoon of fine sea salt to the water and bring to a boil.
As soon as the water bubbles, pour in the rice and set the fire to medium-low. Cook the rice al dente in 15-20 minutes. Put the rice in a sieve and cool in cold running water.
Remove the lemon, celery and bay leaves and drain the rice well before putting it in a bowl.
In the meantime, preheat the oven to 200ºC. Cover a baking tray with baking paper.
Wash the green asparagus. Remove the hard ends and cut the tender parts into pieces of about 2 cm long. Drain the artichoke hearts and cut them through the middle.
Place the asparagus and artichokes on the baking tray. Roast the vegetables (without using olive oil) in the oven for 10 minutes. If using frozen peas, put them in warm water for a few minutes.
Then, drain the peas and stir them through the cooled rice.
Remove the asparagus and artichokes from the oven and leave them to cool before stirring them through the rice as well. Wash the parsley and finely chop both the stem and the leaves with a sharp knife.
Make the dressing by mixing the Dijon mustard, honey, zest and juice of the lemon, sea salt, and olive oil thoroughly with a whisk. Stir the dressing through the rice and vegetables.
Add the finely chopped parsley and season the rice salad with sea salt and coarsely ground pepper.
The salad can be made one day in advance. Keep in mind that it will often need a little more sea salt, pepper, and lemon. Serve the salad lightly chilled or at room temperature.