First ever Thicket Bean (Phaseolus polystachios) harvest

Sorry this isn't actually foraging per se, but the only kind of people who'd grow these are probably foragers anyway. I've been growing them for a couple years, but this is the first year I had enough to bother trying to eat them! From two plants we got about 1/2 a cup.

So my question is, does anyone have any tips for actually eating these things?? We tried soaking them for 24 hours and boiling them for 2 hours, and they were still inedibly bitter! I'm thinking maybe brining them, an alkaline soak, splitting them all in half, and/or swapping out the cooking water a few times. At least one of those ought to work hopefully. It'll have to wait till next year though, we wasted these ones lol.