In a large mixing bowl or bowl of a stand mixer, combine the butter, sugar, brown sugar, salt, and vanilla. Using a mixer beat the mixture until it is smooth, scrapping down the sides a few times.
Add the flour, pecans and water. Beat until combined.
Place the dough on a large piece of parchment paper or plastic wrap. Using your hands, shape it into a log 10 inches long and about 2 inches in diameter. Wrap the dough up and refrigerate until firm, about 2-3 hours.
Preheat oven to 350 degrees. Line a baking sheet with parchment paper.
Unwrap the dough and place it on a cutting board. Using a knife, cut the log into 1/4 inch slices. Arrange the slices 1 inch apart. Bake the cookies for 14-16 minutes, their edges will be golden brown. Repeat with the remaining cookies.
Well the cookies cool, melt the chocolate in the microwave for a minute to a minute and a half, stirring every 20 seconds until melted.
Using a spoon drizzle the chocolate in a zig zag line across each cookie.
Place the cookies in the fridge for 30 minutes so the chocolate can firm up.
Store the cookies in and airtight container.
To Make Ahead: The dough can be refrigerated for up to 5 days To Freeze: The dough can be frozen for up to three months. Defrost before baking.