In a saucepan, melt the butter. Add the sugar, water, honey, and dark rum and cook to 220 degrees F. on a candy thermometer. Add 1 3/4 cups of the almonds and stir while you cook it to hard crack or 300 degrees F. Meanwhile, lay a silpat on a sheet pan or butter a 12 by 18-inch sheet pan well. When the toffee is up to temperature, pour it out onto the pan and place another silpat on top. Roll it to 1/4-inch thick or just spread it with the back of a spoon and let cool.
To temper the chocolate, place it over simmering water, melting it to 115 to 120 degrees F on a chocolate thermometer. Meanwhile, wipe the surface of the toffee with a damp towel to remove any excess butter and let dry for a few minutes. Turn off the heat, remove the bowl from the simmering water, and let cool, stirring until it reaches 82 to 86 degrees. It will begin to set a little around the edges at this point. Return the bowl to the hot (now turned off) water for a few seconds at a time, until it reaches 88 to 91 degrees F. Do not let it go over 91 degrees F or it will go out of temper. Using an offset spatula, spread the surface with the tempered chocolate and sprinkle on the remaining 1/4 cup almonds. Let it set up at room temperature and then break into pieces. Store in an airtight container.