IN THE KITCHEN WITH A GOOD APPETITE, Melissa Clark:   Based on "A Good Appetite," Melissa Clark's immensely popular weekly New York Times Dining Section column, the mission of In the Kitchen with a Good Appetite is threefold. The first is to help home cooks of any skill level create fresh, delicious, and even sophisticated meals with easily available ingredients. The second: to encourage them to improvise their own meals by following Clark's example of experimentation, trial, and error that makes up much of the narrative accompanying the recipes. And the third is to continue to build on the nationwide reader/writer relationship and conversation that's blossomed since the inception of the column.