Line an 8x8 baking dish with parchment paper (spray inside of the pan with oil so the paper sticks).
Roughly chop the almonds and add them evenly to the baking dish.
In a small pan on the stove, add butter, sweeteners, and vanilla extract, over low heat, and stir continuously.
Add candy thermometer, keep stirring, and remove the pan from the heat once the thermometer reaches 290 degrees.
Stir mixture well and pour evenly on top of the almonds.
Place pan in fridge for 5-7 minutes.
Meanwhile, place chocolate in the microwave and melt in 30 second increments.
Remove pan from fridge and drizzle chocolate on top.
Use a spatula to make sure the chocolate covers the entire dish evenly.
Add sea salt flakes.
Return to the fridge for at least an hour.
Once the toffee has completely hardened, lift it out of the pan and break into pieces.
Try not to eat all the toffee in one sitting, it's addicting!
Store in the fridge in an air tight container for a few weeks.