Line 8×11.5 baking dish with aluminum foil and butter the bottom and sides of the pan.
In a skillet, toast the almonds for 3-4 minutes over medium low heat. Roughly chop and set aside.
In a large heatproof bowl, combine , butter, chocolate, 2 cups of marshmallows, condensed milk, vanilla extract and salt. Place it over simmering water (make sure the bottom of the pan doesn’t touch the water) and slowly melt everything until smooth, stirring frequently.
Remove from heat and stir in remaining 1 cup of marshmallows and almonds. Pour it into the prepared pan and leave for at least 2 hours, or overnight to harden. Cut into 24 squares and serve.
Store the fudge at room temperature, or in the fridge, covered, for up to 5 days. You can also freeze this fudge, tightly wrapped, for up to 3 months. When ready to serve, slowly thaw the fudge in the fridge, still wrapped, overnight, then bring it out to room temperature.
For step-by-step photos and additional notes, read the post above.