Step 1Heat the oven to 375 degrees and generously butter 6 (one-half cup) straight-sided ramekins or individual souffle molds. Beat together the goat cheese, thyme leaves, egg yolks and salt until completely smooth.
Step 2Beat the egg whites until frothy. Add the cream of tartar and beat until stiff peaks form, as described in the recipe above.
Step 3Fold about half of the goat cheese mixture into the egg whites, using a hand-held balloon whisk or a spatula. Cut straight down through the puree and the egg whites, scrape the bottom and lift the egg whites over the goat cheese. Turn the bowl a quarter turn and repeat. Keep doing this until the goat cheese is fully incorporated, 4 or 5 times.
Step 4Add the remaining goat cheese and the finely ground walnuts and fold them in the same way. When you're done, the goat cheese should be evenly distributed but there may be small patches of egg white remaining. Do not over-mix.
Step 5Using a large soup spoon, divide the souffle mixture among the ramekins. If you have excess batter, either bake it in another ramekin or discard it. (The recipe can be made to this point and refrigerated or frozen as in the recipe above.)
Step 6Put a jellyroll pan in the heated oven and arrange the souffle ramekins on it. Bake until the tops are puffed and golden brown in spots, 18 to 23 minutes. A sure sign of doneness is when the souffle becomes extremely fragrant. Do not over-bake, or the center will be dry.
Step 7Remove and serve immediately.