Start by opening the can of asparagus and draining them through a sieve. Remember to save the water.
Make a roux by melting the butter over medium-high heat in a heavy-bottomed pot.
Add the flour while whisking vigorously, and once it is well incorporated, add the milk.
Continue stirring, and when it thickens again, add the asparagus water.
Keep stirring the sauce, and when it thickens again, add the cooking water along with your stock cube.
Let it simmer and then add the cream. You might not need to use 1 dl of cream; it depends on how thick your sauce is.
Season with salt, pepper, lemon juice, vinegar, and a bit of sugar.
Add your asparagus pieces and let it simmer for 1 more minute.
The sauce is now ready to serve.
