In Vox it says: "hierba cariofilácea, de hojas blanquecinas y suaves, tallos ahorquillados y flores blancas en panojas colgantes" and gives the scientific name as "Melandrium album", this in turn leads to red and white campion in a Google search, with "Lynchis dioica" and "Silene dioica" as other possible scientific names. As Vox (and Google descriptions) say that the flowers are white, I would say "white campion" (and therefore also don't think it can be a dandelion, which is yellow).

However, do people eat campions?? I haven't found any evidence that they do...

Colleja, on an EU page (first ref) is given the scientific name "Valerianella locusta". Searching for this in Google you get "corn-salad" (which IS edible)(also in the New Shorter Oxford). However, the flowers are not white, they are silver-blue.

So, to sum up, Collins says it's campion - this is a page on campion

http://ghs.gresham.k12.or.us/science/ps/nature/gorge/5petal/...

but plants, etc. are always difficult to translate as there is so much discrepancy. Can the EU page be trusted? I think so. If it was my translation, I'd put corn-salad.
This is the same EU page in English:

http://europa.eu.int/eur-lex/en/lif/dat/1972/en_372L0168.htm...

Another possible name for corn-salad is "lamb's lettuce" (also in New Shorter Oxford)