Preheat oven to 350°F. Place the almonds on a cookie sheet and bake them, stirring occasionally, for 10 to 12 minutes or until golden. Cool completely.
In a food processor with the metal blade, pulse the almonds until they are chopped very finely but not powder fine. Sprinkle half the nuts over a 7-inch by 10-inch area on the prepared cookie sheet. Place it near the range. Also have the vanilla extract and baking soda near the range.
In a heavy, medium size saucepan, preferably with a nonstick lining, combine the brown sugar, water, and butter and, stirring constantly, bring to a boil. Stir often to prevent burning until the mixture reaches 285°F. (the soft-crack stage: Syrup dropped in ice water separates into threads that are hard but not brittle). Immediately remove the saucepan from the heat because the temperature will continue to rise to 290°F., and add the vanilla extract and baking soda. Pour the toffee mixture evenly in a 7-inch by 10-inch rectangle on top of the nuts.
Immediately scatter the chocolate chips over the hot toffee. After about 5 minutes, the chocolate will be soft enough to spread with a long metal spatula in an even layer over the surface of the toffee. Dust the chocolate with the remaining chopped almonds. Let cool, then break into bite sized pieces.
Store in an airtight container at room temperature. Keeps about 1 month, after which it is still delicious but the sugar starts to crystallize. Makes 1 pound.