Indigenous legume crops are pivotal in providing proteins and food security to sub-Saharan African rural communities, but most of these crops are underutilized because of the so-called hard-to-cook (HTC) phenomenon in combination with inadequate processing techniques. This review studies the case of bambara groundnut, which is third in importance after groundnut and cowpea and especially adapted to semi-arid areas. Published data on the HTC phenomenon implicate microstructural and compositional changes as factors leading to its development. Useful and sustainable techniques to process HTC legumes in developing countries include cooking with alkaline salts, milling, roasting, fermentation, and malting. Improvement of these processing techniques in relation to nutrient bioaccessibility, safety, and consumer acceptance of the products is urgently needed. Recommendations are to lessen the problems of food security in sub-Saharan African countries through, amongst other means, the optimization of bambara groundnut processing methods.