arXiv:2610.34669v1 Announce Type: new Abstract: In this paper, we present and analyze an interior penalty discontinuous Galerkin method for Dirichlet boundary control problems governed by the biharmonic equation, with the control imposed through the normal derivative. The method is based on a reconstructed discontinuous approximation that admits an arbitrarily high-order approximation space with only one unknown per element. We construct a discretization that approximates the state and adjoint state in this space and derive a priori error estimates in the energy and $L^2$ norms. The analysis is carried out under the limited regularity available on polygonal domains by means of a medius argument. Numerical experiments are provided to support the predicted convergence rates.