I got some of the Andean species (known there as tarwi and by a few other common names) from the seed bank. They're a cultivated crop with good sized beans. The recommendation for those is to soak in
water starting in the morning, changing the water that night and again the next morning, and then enjoy for dinner. Levels of alkaloids can differ between species and varieties, but that's a basic leaching schedule. The European method takes way longer (like weeks) and is way more convoluted (which may be down to European varieties containing more alkaloids.) At any rate, if they're still bitter after leaching and cooking, toss them and leach the next batch for longer. Leaching time
should be consistent over the
course of an entire batch.
I didn't have irrigation and our drought started 2 months early this year, and I didn't want to risk the seed, so unfortunately I didn't get to grow and try them. Looking forward to giving them a go this coming season.
Bill Whitson of Cultivariable actually recommends the non-sweet varieties, since the alkaloids deter pests and are relatively painless to leach out.
If you search for tarwi I have a post where I posted a couple of cookbooks released by NGOs in Latin America that were aiming to increase the popularity of once popular crops. They include tarwi as well as grains like quinoa and amaranth, and tubers like oca and ulluco. The cookbooks are in Spanish, but they include pictures and are pretty basic recipes that can fairly easily be translated. Especially with a smartphone that can translate text from pictures.