Cook the Book: Chocolate Sablés

Ingredients

• 1 cup cake flour sifted
• 0.5 cup dutch-processed cocoa powder 
• 1 large eggs 
• 1 cup potato flour 
• 1 pinch salt 
• 8 ounces bittersweet chocolate finely chopped
• 0.5 cup sugar for decorating
• 1 cup sugar 
• 1.5 pound butter unsalted room temperature (2 sticks)
• 1 teaspoon vanilla extract pure

Equipment

• bowl
• baking sheet
• baking paper
• oven
• blender
• plastic wrap
• double boiler
• baking pan
• chefs knife

Directions

1. In the top of a double boiler or in a bowl over simmering water, melt the chocolate. When chocolate is nearly melted, remove from heat and stir until smooth. Set aside to cool; return to double boiler only briefly if chocolate begins to set up.
2. In a mixer fitted with the paddle attachment, beat the butter at medium speed until smooth and pale.
3. Add the sugar; continue beating, scraping down bowl sides often, until mixture is completely smooth, 3 to 5 minutes total. Beat in the egg and vanilla until blended.
4. Pour in melted chocolate; mix at medium-low speed just until blended, scraping down bowl sides several times.
5. In another bowl, with a fork, mix together the cake flour, potato flour, cocoa powder, and salt.
6. Add to the chocolate mixture; mix at low speed until just blended. Try not to overmix.
7. Put the bowl of dough in refrigerator; chill for 10 to 20 minutes—until firm enough to handle but not too stiff.
8. Transfer dough to a lightly floured surface. By hand, press dough into a log about 15 inches long and 2 1/2 inches in diameter. (If dough is too tacky, loosely wrap in sheet of plastic wrap to form roll.)
9. Spread the crystal sugar on a baking tray.
10. Place the log (with plastic wrap removed) in sugar; roll to evely coat all surfaces except ends. Wrap well in plastic wrap; chill until firm, at least 4 hours or up to 3 days. Log can also be frozen.
11. Position 2 racks in middle of oven; preheat to 350°F. Have ready 2 cookie sheets lined with parchment paper or Silpat nonstick baking mats.
12. Remove dough from refrigerator; let sit for about 10 minutes, until warm enough to slice evenly. Using a thin-bladed chef's knife, cut log into 1/4-inch slices.
13. Transfer slices to prepared cookie sheets, leaving 1-inch space between each.
14. Bake 10 to 12 minutes, until tops are dull. Cool on wire racks. Can be stored in airtight container up to one week.