Preheat oven to 375°F. For the dough, with a hand beater, or stand mixer, combine the eggs and oil. Add in the flour, baking powder, and sugar. Add in flavorings either for almond or orange biscotti. The dough should be slightly sticky and thick. Split the dough into two balls.
On a 2 baking sheets with parchment paper, place each slab of dough. Using your hands and a rubber spatula, form the slabs into a large rectangle with the thickness of the dough being around ½ Inch. The width of the dough will be how long your cookies are so make as long or short as you want. Bake for 25-30 minutes until it looks golden.
Let the giant cookies cool for a few minutes until it's easier to handle. With a sharp knife, cut into 1/2-1 Inch slices. You should get at least a dozen out of each big cookie.
Place the cookies back onto the baking sheet and bake for another 6 minutes on each side to lightly toast them.
After cookies are cooled, melt the chocolate in the microwave in 30 second intervals, mixing after each session until the chocolate is fully melted. Mix in the butter or shortening to thin it. Once it drizzles off the spoon, it's the right consistency.
Depending on how you want to decorate, you could either lay the cookies out on parchment and run your spoon over them to drizzle the chocolate on top or dip one side of the cookie into the chocolate.
Add your choice of toppings, whether it's orange zest or sliced almonds. Let the chocolate harden. Store in a tin to maintain it's crispiness.