How to keep frozen beans soft? I like putting beans (e.g., mung beans, red beans) into my ice cream when I make ice cream at home.

What I do: soak the beans overnight, boil them, mash them, then mix them into the cream as it's being beaten, then freeze the entire mixture before enjoying.

The problem is that, after freezing, the beans turn into VERY hard bits! They're so hard, it's like I'm biting into crunchy pieces of nuts! I buy the same types of ice cream from the store and their beans don't exhibit this problem. Theirs are soft and chewy.

I'd like for my beans to be soft and chewy when my ice cream comes out of the freezer as well. How is it done?
I think some fats may help better than just sugar? I have never tried this but it is worth the experimentation. If you add heavy cream (dairy) it may help. Coconut cream is high in fat and could also help in keeping it soft at lower temperatures. It is the ice crystals that make it hard, so the key is to separate the ice crystals at the microscopic level. Fat droplets can help in that if they are mixed well. 

If not, just work with some scentless cooking oil in small quantities. As @Ecnerwal mentioned, read through the ingredients of the store bought ice cream and see what other ingredients are present that you may not have in your recipe. Based on some mung bean recipes online, it appears that egg  yolks also help with the texture. Good luck!