There has been a recent surge in methods targeting the recovery of a speed-of-sound map from pulse-echo ultrasound measurements. We focused in this work on a particular technique and identified a drawback shared by similar methods - namely the necessity of a high number of insonification - that we aim to circumvent. To do so, we first propose a beamforming procedure based on the transformation of radio-frequency data into a receive plane-wave basis. A method for extracting the local aberration phase difference caused by speed-of-sound variations is then presented. The speed-of-sound map can ultimately be recovered by inverting a measurement model. Preliminary results show that the proposed method is able to recover quantitatively similar results - a slight reduction of root-mean-square error from 9.35 m/s to 6.95 m/s on simulated data compared to an implementation of the reference method - while requiring 21 plane waves instead of 111.