Lightly grease (or line with parchment) two baking sheets
Combine the vanilla, baker's ammonia, and salt in a very small bowl
Stir to dissolve the ammonia; the salt won't fully dissolve
Combine the vanilla mixture with the butter and sugar, and beat till smooth
Mix in the flour; the mixture will seem quite dry at first
Continue beating until the dough comes together
Break off pieces of dough about the size of a shelled chestnut (about 3/4 ounce)
Roll the pieces into balls
Space them on the prepared baking sheets, leaving 2" between them
For somewhat sweeter cookies with the added crunch of sugar topping, roll them in coarse or granulated sugar before placing them on the baking sheets
Use the bottom of a glass, dipped in sugar if necessary to prevent sticking, to flatten the balls to about 3/8" thick
If you have it, use the end of the food pusher from a food processor; many of these have a circular, ridged pattern on their end, which imprints the cookies with a nice design
Bake the cookies until they're a very light golden brown around the edges, about 25 minutes.
Remove them from the oven, and transfer them to a rack to cool
To dip cookies:
Crush the pecans finely, either by putting them in a zip-top plastic bag and pounding, or in a food processor
Combine the chocolate chips and vegetable oil in a microwave-safe cup
Microwave till the chocolate softens, then stir till it melts completely
Use a pastry brush to paint the bottom of each cookie with chocolate
Dip in the crushed nuts
Place cookies, chocolate-side up, on a piece of parchment or cookie sheet to set