Preheat the oven to 300°F. Lightly grease (or line with parchment) two baking sheets.
1) 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.
2) Mix in the flour; the mixture will seem quite dry at first.
3) Continue beating until the dough comes together.
4) Break off pieces of dough about the size of a shelled chestnut (about 1/2 ounce); a teaspoon cookie scoop works well here. Roll the pieces into balls. Space them no the prepared baking sheets, leaving 1 1/2" between them.
5) 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.
6) 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.
7) Bake the cookies until they're a very light golden brown around the edges, about 25 minutes.
8) Remove them from the oven, and transfer them to a rack to cool.
9) To dip cookies: Crush the pecans finely, either by putting them in a zip-top plastic bag and pounding, or in a food processor.
10) Combine the chocolate chips and vegetable oil in a microwave-safe cup. Microwave till the chocolate softens, then stir till it melts completely.
11) Use a pastry brush to pain the bottom of each cookie with chocolate.
12) Dip in the crushed nuts.
13) Place cookies, chocolate-side up, on a piece of parchment or cookie sheet to set.
Yield: about 4 dozen cookies.