In a heavy saucepan over medium heat, add brown sugar and salted butter. Stir often until mixture is bubbly and thick and candy thermometer registers 280F. ( This may take 10 or so minutes )
Once temperature reaches 290F, immediately remove from heat.
Add 3/4 cups almonds to the mixture and stir to c ombine well.
Pour evenly into a rimmed 18x13 baking sheet. ( no need to oil or butter the pan )
Use the back of a wooded spoon or my favorite tool, an offset spatula to quickly smooth mixture evenly into pan. Work quickly since candy sets quickly.
While toffee cools, melt chocolate.
Spread chocolate evenly onto top of toffee, taking care to smooth the surface.
Sprinkle with remaining chopped almonds.
Chill in refrigerator for a couple of hours to cool completely. Once cooled, carefully cut toffee
into pieces with a sharp knife.
Candy keeps well in an airtight container.