Preheat your oven to 350 F degrees.
In a large bowl add the butter, sugar, brown sugar, ginger and allspice, then beat on medium until well combined. Add the eggs and mix until well combined. Add the molasses and continue mixing for another 30 seconds until well mixed. Add the flour, baking powder, salt and beat on low until well mixed. Stir in the pistachios and the currants.
Transfer the dough onto your work surface and divide the dough into two pieces. Shape each half into a rectangle that's about 10 inches in length and about 4 to 5 inches in width. Flatten each piece slightly.
Place the logs onto a cookie sheet, making sure there's a couple inches in between them. Bake for 22 to 25 minutes or until lightly browned around the edges and the tops are cracked slightly. Remove the baking sheet from the oven and let it cool for about 15 minutes.
Reduce the oven temperature to 325 F degrees.
Transfer the logs to a cutting board and using a serrated knife slice them diagonally into 1/2 inch to 3/4 inch slices. Place the slices, cut-side down back onto the baking sheet.
Bake for 9 more minutes, turn the cookies over and bake for another 7 minutes. The cookies should be crispy at this point. Transfer to a wire rack and cool completely.
Add the English toffee candy melts to a medium size bowl and microwave for 1 minute. Stir using a spatula, then place in the microwave for another 30 seconds. Stir again, it should be melted and smooth, if it isn't, place it in the microwave again for another 15 seconds if needed.
Dip each biscotti cut side down in the English toffee, and lay back on the rack with the candy side up. Repeat with all the biscotti. Let them set at room temperature until the candy coating is firm.