Melt chocolate in a double boiler until smooth.

Prepare a muffin pan with 10 liners (lightly greased).

Add melted chocolate to each liner. Spread evenly in each liner. (Use about 2/3 of the total chocolate)

Place muffin pan in the freezer and allow chocolate to set.

Combine butter and monk fruit sweetener in a saucepan over medium heat. Stir constantly until sweetener is completely dissolved.

As the mixture begins to thicken add the liquid stevia and chopped nuts.

Remove the muffin pan from the freezer and spoon toffee mixture into each cup - spreading evenly between each liner.

Return muffin pan to the freezer.

Reheat remaining chocolate. 

Once melted remove muffin pan from the freezer and cover toffee with remaining chocolate.

Place back in the freezer for the final set.