One possible solution could be to candy the herbs (though it’s a lot of work) or to soften the toffee by turning it into a kind of cream, freezing it separately, and then folding it into the ice cream at the last moment. This challenge is addressed in the article,
>We need to add sugar to the fruit to make sure it is softer than the ice cream itself – you don’t want to bite into ice cream and find a hard, frozen berry.
and considering you almost never see artisanal ice creams with chunks (unlike industrial ones like Ben & Jerry’s, for example), this is where culinary engineering becomes essential I guess.
I'm also not a fan of ice cream with solid stuff. If you can't lick it pleasurably, it's not really ice cream in my book.
Similar to this: https://www.seriouseats.com/dave-arnolds-thai-basil-daiquiri...
The obvious solution to this is to make an syrup infusion and use that instead of sugar or as a topper.
I make herb and floral syrup all the time. I do 1 cup water, 1 cup sugar, handful of herbs. Heat and simmer for around 10 minutes. Strain.