Make sure your butter and eggs are at room temperature before beginning.
Preheat the oven to 350º.
Add slivered almonds to a baking sheet and lightly toast for about 2 minutes, until just fragrant but not browning.
Remove from heat and set aside to cool.
In a large bowl, combine cake mix, flour, butter, vanilla extract, and eggs.
Dough may be slightly crumbly.
Add in almonds and knead the dough until it comes together.
Don't over knead.
Prepare 2 large baking sheets with parchment paper.
Split into two logs
.
On a parchment lined baking sheet
, flatten each log half into a 12 by 24 inch log.
Leave about 3 inches between each log
in case they spread a little.
Bake for 25 minutes or until an inserted toothpick comes out clean.
Cool on cookie sheets for 20 minutes.
Remove the logs from parchment and place on a cutting board.
Slice each log diagonally with a serrated knife. Each piece should be about a half-inch wide.
Flip the slices to cut side down.
Place back in oven for 10 minutes or until bottoms are light golden brown.
Cool on cookie sheet for 2 minutes
.
Transfer to a wire cookie rack and let cool completely.
Just before dipping the biscotti, melt chocolate in a double boiler or in the microwave. If using the microwave (easy method!) do it in 15 second increments until the chocolate is melted. Otherwise you may end up with a mess you can't use.
Dip biscotti ends in melted white chocolate.
Sprinkle with sliced almonds.
Store the biscotti in airtight container.