China Southern Airlines offers some good solution from Benelux to Hong Kong. Return flights from Amsterdam are now available from €324 incl. all taxes and checked luggage. The cheapest solution is available when travelling on weekdays (Monday to Thursday) but also adding some weekend options. You would have to accept a bit longer layover in Beijing on your way back so consider to book free stop-over and visit both cities at once..
If interested in this solution with China Southern Airlines please look for flights in travel period from 7th of November to 12th of December 2017 then 8th to 23rd of January to or 5th to 15th of March 2018. (Latest date of your outbound flight to Hong Kong). Blackout period around Christmas Holidays. Promotion is running till 15th of November or valid until sold out..
Booking samples
Amsterdam - Hong Kong from €324
Amsterdam - Hong Kong - Beijing - Amsterdam from €349
Travel date samples
10. - 23.11.
13. - 27.11.
19.11. - 3.12.
26.11. - 10.12.
11. - 26.12.
12. - 26.1.
13. - 27.1.
20.1. - 3.2.
25.1. - 5.2.
5. - 21.3.
8. - 23.3.
12. - 25.3.
15. - 28.3.
Booking sample of cheap return flights from Amsterdam to Hong Kong from €324 here. In this case you would fly from The Netherlands to Hong Kong on 20th of January. Your return flight from Asia back to Europe would be two weeks later on 3rd of February 2018.