I just mix together some oats, honey, water, and some sugar, bake it until it's nice and golden (I would rather have it a little undone than having the horse eat burnt stuff). Cut it into small pieces and that's it!
I have a recipe called the 3-2-1 Snacks
It is 3 parts steel cut oats
2 parts sugar
And 1 part water
Let them harden overnight and they last quite sometime!