Read the recipe in full, as well as looking at the photos below this recipe, before beginning. Doing both will help get you started.
Preheat oven to 300°F (149°C). Line two large baking sheets with parchment paper or silicone baking mats. Spread almonds on one sheet (keep the other one set aside) and toast for 15 minutes, stirring twice during that time. Remove toasted almonds from the oven and turn the oven up to 350°F (177°C). Rinse/wipe off the one baking sheet so you can use it again for the biscotti.
Pulse the toasted almonds in a food processor or blender until very coarsely chopped. Set 1 cup of chopped toasted almonds aside. Pulse the remaining chopped toasted almonds until they are a little more fine. These will be what you sprinkle on top of the chocolate. Set them aside too.
In a large mixing bowl, whisk flour, brown sugar, baking powder, cinnamon, and salt together. Using a pastry cutter or 2 knives, cut in the butter until the mixture is crumbly. Gently toss in the 1 cup of coarsely chopped almonds. Set aside. In a medium bowl, whisk the eggs, oil, and vanilla together. Pour into the flour/butter mixture and gently mix with a large wooden spoon or rubber spatula until everything is just barely moistened.
Turn dough out onto a lightly floured surface, and with floured hands, knead lightly until the dough is soft and slightly sticky, about 8-10 times. If it’s uncontrollably sticky, knead 1-2 more Tablespoon(s) of flour into the dough. With floured hands, divide the dough in two and place each half onto a baking sheet. Shape each half into an 8-9 inch long roll, patting down until each is about 1/2 inch thick. Using a pastry brush, lightly brush the top and sides of each biscotti slab with egg wash.
Bake in batches (or together) for 25-26 minutes, or until the top and sides of the biscotti slabs are lightly browned. Remove from the oven, but do not turn off the heat. Allow to cool for 10 minutes. Once the slabs are cool enough to handle, cut each into 1 inch thick slices. Set slices cut sides upright, ¼ inch apart, on the baking sheets. Return to the oven to continue baking for 9 minutes. Turn biscotti over and bake other side for 9 minutes. The cookies will be slightly soft in the centers with harder edges. Remove from the oven and allow to cool for 5 minutes on the baking sheet. Then transfer to a wire rack to cool completely before dipping in chocolate. As the biscotti cools, it becomes crunchy. Save the baking sheets for the next step.
Melt the chocolate in a medium bowl in the microwave (or use a double boiler). The key to melting chocolate in the microwave is to do it in small bursts and stir frequently. Chocolate seizes so fast, so easily. Melt in 15 second increments, stirring vigorously with a spoon after each increment, until completely melted and smooth. Dip one side of each biscotti cookie in the melted chocolate and immediately sprinkle with the remaining toasted almond crumbs. I do this over the sink to avoid a mess! Place the dipped biscotti back onto the baking sheets and allow chocolate to set in the refrigerator or at room temperature, about 30-45 minutes.
Make ahead tip: Store leftover biscotti in an airtight container for up to 2 weeks. Biscotti may be frozen up to 3 months, but I suggest freezing without the chocolate coating.