A note on making raw soups: For your blender, the easiest thing to use is boneless, skinless chicken breast. Cut it into smaller pieces and the blender should handle it fine. Boneless pork chops aren’t too bad either. Liver is very soft already so you don’t even need to chop it ahead of time, and hearts are generally easy to blend. Then use powdered eggshell for the calcium. Granted this is all for soup.
If you are going from grinds to chunks, it is easiest to just start with slivers of meat. So buy boneless meat (or if you really want to do the extra work, cut the meat off the bones and use the bones to make soup broth for humans or some bone broth) and cut the boneless meat into slivers. Mix the slivers into the ground raw, and gradually increase the size and number of the meat slivers while decreasing the ground meat. You can add heart and organ slivers in there at the same time, or you can work on hearts and organs separately via the organ soup method (see below). Once they are eating decent sized chunks (use eggshell in the meanwhile), you can start on the bones. Mash up some chicken wings (easiest to start with since the bones are nice and small) with a hammer or meat cleaver. Mix the chunks of bone in, you may need to hand feed at first, and as their jaw strength increases gradually increase the bone size (smash/chop it less and less).
For organ soup method, you can start with a blended meat and heart and organ soup for about 6 meals a week (work on the chunks the other 8 meals). You can do this at the same time as the other stuff. Gradually increase the organs and hearts in the soup while decreasing the meat. When you get to a soup that is about 1/2 organ and hearts and 1/2 muscle meat, drop down to 4 meals a week. Continue to increase the organ and heart and decrease the muscle meat, at the same time starting to add in small chunks of organs and hearts. Slow and steady wins the race. Increase the chunk size and the organ/heart amount, and decrease the soup amount overall, until they are eating hearts and organs without soup. You can slowly separate hearts and organs at the same time as all of this as well (2 meals organ heavy soup, 2 meals heart heavy), or at the same time by having mixed-chunk soups. When you get down to no muscle meat needed (all hearts and organs), drop down to 3 meals a week. Eventually you should have them eating one and a half meals of organ and one and a half meals of heart each week. The easiest way to do this is:
AM: Organs (half liver, half other organs)
AM: half heart, half organs (liver or half liver half other organs)
PM: bone-in meal
Depending on your ferrets, you will likely have to spread those 3 meals out over the week instead of one right after the other as these meals are rich.