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The one-loop corrections to the weak mixing angle $\sin^2\theta_{eff}^b$derived from the $Z{\bar b}b$ vertex, are known since 1985. It took another 30years to calculate the complete electroweak two-loop corrections to$\sin^2\theta_{eff}^b$. The main obstacle was the calculation of the O(700)bosonic two-loop vertex integrals with up to three mass scales, at $s=M_Z^2$.We did not perform the usual integral reduction and master evaluation, butchose a completely numerical approach, using two different calculationalchains. One method relies on publicly available sector decompositionimplementations. Further, we derived Mellin-Barnes (MB) representations,exploring the publicly available MB suite. We had to supplement the MB suite bytwo new packages: AMBRE~3, a Mathematica program, for the efficient treatmentof non-planar integrals and MBnumerics for advanced numerics in the Minkowskianspace-time. Our preliminary result for LL2016, the "dessert", for theelectroweak bosonic two-loop contributions to $\sin^2\theta_{eff}^b$ is:$\Delta \sin^2\theta_{eff}^{b(\alpha^2,\rm bos)} = \sin^2\theta_W ~\Delta\kappa_b^{(\alpha^2,bos)}$, with $\Delta\kappa_b^{(\alpha^2,bos)} =-1.0276 x 10^{-4}$. This contribution is about a quarter of the correspondingfermionic corrections and of about the same magnitude as several of the knownhigher-order QCD corrections. The $\sin^2\theta_{eff}^b$ is now predicited inthe Standard Model with a relative error of $10^{-4}$ [1].

30 years, some 700 integrals, and 1 dessert, or: Electroweak two-loop corrections to the Zbb vertex