Flow of concentrated soft materials like molten chocolate often has the ambiguity of behaving like a solid or a liquid depending on the external constraints. Determination of the constitutive law is often unreliable and consequently the yield stress value too. This difficulty of determining yield stress, particularly when using a standards protocol such as the IOCCC for chocolate, is a consequence of the presence of wall slip. Most attempts to assess slip velocity using Yoshimura and Prud'homme's method have resulted in failure. We propose to tackle this problem by using an easy and reliable methodology applied to a commercial chocolate in a melted state with, as equipment, a plate-plate rotational rheometer. This method allows precise determination of the yield stress value, the constitutive law and the slip velocity, as well as also providing an explanation to the apparent Newtonian plateau and thickening behavior of the raw flow curve.