Preheat the oven to 350 degrees F. Line a cookie sheet with parchment paper. Set aside.
Sift the 1 to 1 flour, tapioca, brown rice flour, baking powder, cocoa powder, and salt together. Resift a second time.
In a double boiler or over very low heat in a heavy bottomed saucepan, melt the chocolate and butter, stirring often.
In a stand mixer bowl, beat the eggs with the sugar until very thick and lemon colored. Mix in the melted chocolate mixture on low speed. Stir in the flour mixture on low speed.
Form the dough into two logs on a lightly gluten free floured board, about 2 ½ or 3” wide x 9” long, and about 1 ½ inches high. Set the logs at least 2 ½ inches apart on your prepared baking sheet. Bake for 28 – 32 minutes until logs are set. Cool for ½ hour to 45 minutes before proceeding.
Slice each log on a diagonal into ½ “ thick slices, very carefully with a sharp knife. Place the slices on another parchment lined cookie sheet.
Set oven temperature to 275 degrees F.
Bake the slices for 20 minutes before turning over and baking for another 20 minutes. Cool on the cookie sheet for 20 minutes before moving to a wire rack to finish cooling.
Once the cookies are completely cool, melt the dark chocolate over a double boiler until it is not quite melted all the way. Remove from the heat and stir to finish melting. Add the 2 teaspoons of oil and stir completely through the chocolate.
Melt the white chocolate in a microwave safe bowl in 20 second intervals until it is beginning to melt at the bottom and the edge. Finish melting by stirring. Add the oil and stir to distribute.
Dip one end of the biscotti in the dark chocolate about 2-2 ½ inches up the cookie. Set on a piece of foil on a cookie sheet or board to dry. Once you have about 6 cookies dipped, drizzle some white chocolate over the dark chocolate. Repeat for remaining cookies. Or you can dip several of the cookies in white chocolate and dip the others in the dark chocolate. Adjust the amounts of white and dark chocolate as desired.
Store in a sealed air-tight container for up to two weeks, for best crisp texture.