There is no requirement in the EPC that the claimed invention may be carried out with the aid of only a few additional non-disclosed steps. The only essential requirement is that each of those additional steps be so apparent to the skilled person that, in the light of his common general knowledge, a detailed description of them is superfluous (TÂ 721/89).
Source: http://www.epo.org/law-practice/legal-texts/html/caselaw/2019/e/clr_ii_c_6_6_5.htm
Date retrieved: 17 May 2021