Texas Sheet Cake

Instructions

1. 1

   Heat the oven and prep the pan

   Set a rack in the middle of the oven and heat to 350°F. Grease an 18x13-inch half sheet pan generously, including the corners and the inside walls. Don't line it with parchment — you want the batter to climb the sides of the pan so the cake bakes level.

2. 2

   Whisk the dry ingredients

   In a large bowl, whisk the flour, granulated sugar, baking soda, and salt until no streaks remain. Use a bowl bigger than you think you need; you're about to pour a pan of boiling liquid into it.

3. 3

   Boil the butter, water, and cocoa

   In a medium saucepan over medium heat, combine the butter, water, and cocoa powder. Stir as the butter melts, then bring it to a full rolling boil and let it bubble for about 30 seconds. It may look slightly grainy or separated — that's fine. Pull it off the heat.

4. 4

   Combine hot and dry

   Pour the hot cocoa mixture over the dry ingredients and stir with a sturdy spatula or beat briefly with a hand mixer on low until smooth. The heat is doing real work here: it blooms the cocoa for deeper flavor and partially dissolves the sugar, which is what gives this cake its dense, almost-brownie crumb.

5. 5

   Add the buttermilk, eggs, and vanilla

   In a measuring cup, stir together the buttermilk, beaten eggs, and vanilla. Pour into the chocolate batter and mix just until uniform — about 30 seconds. The batter will be thin and pourable, closer to a thick hot chocolate than a cake batter. Stop mixing as soon as it's smooth; overworking it now makes the cake tough.

6. 6

   Bake

   Pour into the prepared pan and tilt it gently to spread the batter into the corners. Bake 18 to 22 minutes, until the surface looks matte and springs back when you press it lightly and a toothpick in the center comes out with a few moist crumbs. This cake is thin and goes from done to dry quickly, so check at 18 minutes.

7. 7

   Start the frosting before the cake is out

   When the cake has about 6 minutes left, combine the butter, cocoa, and milk in a medium saucepan over medium heat. Stir constantly until the butter melts and the mixture comes to a simmer, then remove from the heat. Whisk in the powdered sugar a cup at a time, then the vanilla and salt, until glossy and smooth. Timing matters — this frosting needs to be hot when it meets a hot cake.

8. 8

   Frost immediately

   The moment the cake comes out of the oven, pour the warm frosting over it in wide ribbons, starting at the edges and working in. Spread quickly with an offset spatula, using as few passes as you can. It sets up fast, and if you fuss with it after it starts to firm you'll drag up cake crumbs. Scatter the pecans over the top right away so they stick.

9. 9

   Cool before cutting

   Let the cake sit at room temperature for at least 1 hour. The frosting goes from glossy to a dull, fudgy sheet as it sets, and that's your cue it's ready. Cut into 24 squares with a thin knife, wiping the blade between cuts.

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Baker's Tips

• 1.

  Toast the pecans on a dry sheet pan at 350°F for 6 to 8 minutes before chopping. It takes almost no time and makes an enormous difference against all that sweetness.

• 2.

  No buttermilk? Stir 1 1/2 teaspoons of lemon juice or white vinegar into 1/2 cup of whole milk and let it sit for 10 minutes. Sour cream thinned with a splash of milk works too.

• 3.

  Have the frosting ingredients measured and the saucepan ready before the cake goes in. The window between pulling the cake and pouring the frosting should be under a minute.

• 4.

  Dutch-process cocoa gives a darker color and smoother, less acidic flavor; natural cocoa gives a sharper, more old-fashioned chocolate tang. Both work, so use what you have.

• 5.

  If your frosting stiffens before you finish spreading, whisk in warm milk a teaspoon at a time until it loosens.

• 6.

  Baking in a 9x13-inch pan instead will give you a much thicker cake — add 10 to 15 minutes and check the center carefully.

• 7.

  This genuinely improves overnight. The crumb settles and the frosting fuses into the top, so make it a day ahead when you can.

Equipment

• 18x13-inch half sheet pan
• Medium saucepan (2-quart)
• Large mixing bowl
• Whisk
• Offset spatula
• Liquid measuring cup

Storage