How to Make It
Line an 8-by-11-inch baking pan with foil. Spray the foil with vegetable oil. In a heavy saucepan, melt the butter. Stir in the sugar and water and bring to a boil. Wash down the side of the pan with a moistened pastry brush. Cook over moderate heat, stirring with a wooden spoon, until a deeply golden caramel forms and the temperature reaches 300° on a candy thermometer, 15 minutes; if the sugar and butter separate, stir vigorously to blend. Remove from the heat and add the coarsely chopped almonds, vanilla and salt. Scrape the toffee into the prepared pan; let cool for 10 minutes.
Sprinkle half of the chocolate over the toffee and let stand until melted. Spread the chocolate over the toffee and sprinkle with half of the finely chopped almonds. Freeze the toffee for 10 minutes.
Invert the toffee onto a foil-lined baking sheet and peel off the foil backing. In a microwave safe bowl, melt the remaining chocolate. Spread the melted chocolate over the top of the toffee and sprinkle with the remaining finely chopped almonds. Let the toffee cool, then break into shards.