1. Grate the cheddar cheese into a 2 quart bowl. I grate 1/2 of it real fine, then the rest coarse.
2. Chop the onion real fine, and add it to the bowl.
Prepare the chilli peppers by first cutting in half, then removing the seeds and membrane, the membrane is where most of the heat is. Chop these real fine then add to the cheese.
3. Add the cream cheese, then half of the mayonnaise, and mix well. continue adding mayonnaise until it just comes together, then add the blacken.
Note: You can make this up to a week ahead of time, but do it at least a day ahead to let the flavors blend.
4. Prepare the pickles by cutting them in half, lengthwise, then scoop out the seeds with a small spoon, the smaller the better. I actually used a metal measuring spoon that's called a "dash". Be careful that you don't go all the way through the pepper. As you finish them, set them, cut side down, on paper towels to drain. Using a real sharp knife, carefully cut a very thin slice from the bottom of each half to let them sit flat on a plate. Cut each pickle half in half to make bite sized pieces.
Note: If you're doing these the day ahead for a party, don't bother setting the pieces on paper towels, just set them back in the jar with the brine, until your ready to use them.
5. You can fill the pickles up to 2 hours or so ahead of service. Just store them in the refrigerator until you're ready to serve.