I know a group of dogs of the same litter. A couple of weeks ago it was their birthdays, and I thought about exactly this. The kids thought about disgusting dog-food "cakes"...
These little-biccies went down well with all dogs offered (but then so did the stinky cakes...)
Step 1: Ingredients
These are simple, you don't need much:
Liver (I bought 99p worth of ox-liver)
Oil (I used redundant olive-oil from a jar of anchovies)
Step 2: Make biscuit-dough
Turn your oven on at a temperature around 150oC / 300oF now.
Chop the liver into small pieces. 200g / 7oz, this helps to deal with "stringy" bits.
Blend with the oil. 25g / 1oz, and by "blend" I mean to use power-driven metal blades, to liquidse the lumps.
Add 2tsps of baking powder to 150g / 51/4oz plain flour.
Mix the flour & baking powder into the homogenised liver and oil, until you have a thick and sticky pink dough.
Turn the dough onto a floured-surface and roll / stretch into a sheet.
Cut into strips.
*Note this will be soft, and sticky - use plenty of flour.
This is a small prep', if I'd used all the liver:
liver 520g / ~18.5oz
flour 390g / ~14oz
oil 70ml / ~21/2floz
baking powder 5tsp
Step 3: Bake biscuits
For long-life, biscuits need to be dried-out, cook slowly and gently.
I used 60 min at 150oC / 300oF turning once after 30 min, and then I turned the oven off leaving the biscuits in the oven with the door ajar as it cooled.
They turn out light and crunchy, tasting and smelling like cooked-liver.