How can peanut brittle be made softer?
Cooking the peanut brittle for a shorter amount of time will result in a softer and more chewy result however it will be very sticky. So much so that it may be difficult for your grandparent to eat (think of very chewy caramel). This would be made worse if they had dentures or partials that might prevent them from eating candy like that. You could try lightly heating pre-made peanut brittle in a humid area (perhaps boil some water and let the steam warm it) – that might warm and rehydrate it slightly which could help. But I suspect that the taste would be affected and it might just turn into a soggy and sticky mess. You might be able to try something like grinding peanut brittle down into nearly a powder and then adding it to vanilla ice cream or yogurt (or even finding pre-made peanut brittle ice cream). That might get it into a state that’s easier for your grandparent to consume but still retains the flavor.