Step 1Pat the pork chops dry and sprinkle both sides with salt to taste. Slash the fat along the edge of each chop through to the meat in three places. This will help keep it from curling while it is cooking. Cut a pocket in each pork chop nearly to the bone and almost the length of the chop, leaving only about one-fourth to one-half inch of meat uncut at either end.
Step 2Toast the walnuts in a small dry skillet over medium heat until they begin to brown and turn fragrant, 3 to 5 minutes. Keep stirring them to keep them from scorching. Set aside to cool.
Step 3Combine the toasted walnuts, blue cheese and shallots in a small bowl, and stir with a fork to mix thoroughly. Spoon 1 to 1 1/2 tablespoons of filling into the pocket of each pork chop. Reserve the remaining filling. Press the sides of the pocket together and seal them closed by threading a toothpick through both sides.
Step 4Melt the butter in a large skillet over medium-low heat. When the foam has subsided, add the pork chops and cook until lightly browned on one side, about 5 minutes. Carefully turn and continue cooking on the other side until it is similarly browned, another 5 minutes. Pay attention to the heat: If the butter begins to turn too brown, reduce the flame to keep it from scorching.
Step 5When the chops are browned, remove them to a plate and cover them with another plate to keep them warm. Pour off the fat from the skillet and place the skillet over high heat. When all of the meaty bits that have stuck to the bottom of the pan turn brown (about 2 minutes), add the Cognac and cook until it reduces to less than one-fourth cup of light brown liquid; there should be almost no harsh smell of alcohol remaining. This will take only a couple of minutes.
Step 6Reduce the heat to medium-low and whisk in the creme fraiche. When the creme fraiche begins to bubble around the edges, whisk in the reserved filling and the thyme. When the liquid begins to bubble again, return the pork chops to the pan and reduce the heat to low.
Step 7Cook, covered, about 3 to 4 minutes on each side. When the pork chops are done, a paring knife should penetrate the meat fairly easily. Keep an eye on the liquid and if it begins to reduce too much, lower the heat again. Before serving, taste the sauce and add a little black pepper and a dash of salt if necessary (it probably won't be, but some blue cheeses are saltier than others). Remove the chops to a platter, remove the toothpicks and ladle the sauce over the top. Serve immediately with a green salad on the plate.