Preheat oven to 375 degrees. Grease cookie sheets or line with parchment paper.
In a medium bowl, beat together the butter, eggs, sugar, and almond extract until well-blended.
Combine the flour and baking powder. Stir into the egg mixture to form a heavy dough.
Divide dough into two pieces. Form each piece into a roll as long as your cookie sheet.
Place roll onto the prepared cookie sheet, and press down to 1/2 inch thickness. (This can be tricky because it is a wet dough, but keep at it.)
Bruch egg wash on top of each roll.
Bake logs for 25-30 minutes, rotating once during the baking time. The logs will be firm to touch when baked. Allow to cool on trays for at least 15 minutes.
With a sharp serrated knife, slice each log into 1/2-inch slices
Lay the slices onto the parchment lined tray and bake for 20-30 minutes. (Cookies will not spread any longer.) Rotate the trays halfway through the baking time to ensure the biscotte bake evenly.