3/4 stick (6 tablespoons; 3 ounces; 85 grams) cold unsalted butter, cut into small cubes
1/4 teaspoon pure vanilla extract
To make the streusel: Put the flour, sugar and salt in a medium bowl and mix everything together by running the ingredients through your fingers. Drop in the butter and squeeze and rub the cubes into the mixture until you have a sandy mix. If you press a little streusel together, you'll get lumps, which is just what you want. Drizzle the vanilla over the streusel and toss, squeeze and rub to distribute it. Cover the bowl and chill the streusel until needed. (You can make the streusel up to 1 week ahead; pack it in an airtight container and keep it refrigerated.)
"Baking Chez Moi" by Dorie Greenspan (c) Houghton Mifflin Harcourt 2014. Provided courtesy of Dorie Greenspan. All rights reserved.