Step 1: Finely slice that red onion and mix in a bowl with the vinegar and a little salt.
Step 2: Bring a small saucepan to boil over a high heat.
Step 3: Gently lower the egg into the pan of boiling water and leave to boil for about 8 minutes.
Step 4: Place the pan under a cool-running tap and allow the cold water to cool the egg (this prevents the yolk from turning grey, and stops the cooking process). Then, place the egg on the side.
Step 5: Bring the same pot to boil and throw the asparagus in for about 5 minutes.
Step 6: Drain the vinegar from the onion bowl into a cup and add in the mustard and olive oil. Whisk thoroughly to create a smooth, delicious salad dressing.
Step 7: Lay the rocket out on a plate with the asparagus on top along with the onion.
Step 8: Peel and quarter the egg and lay that onto your evolving salad.
Step 9: Drizzle with your delicious dressing and season with a little salt and pepper. You are ready!