Peanut Butter Cookies with Blackberry Jam - from Sally

These Giada de Laurentis cookies come highly recommended from Sally. I have not made them (since I don't like peanut butter - yes, I know I'm unAmerican) but Sally said they were excellent!

Peanut Butter Cookies with Blackberry Jam
Ingredients:
1 cup all-purpose flour
1/3 cup unsweetened cocoa powder (recommended: Hershey's)
1/2 teaspoon baking soda
1/8 teaspoon fine sea salt
1 stick (1/2 cup) unsalted butter, at room temperature, cut into 1/2-inch pieces
3/4 cup creamy peanut butter, at room temperature
3/4 cup sugar, plus 1/4 cup
1/2 packed cup light brown sugar
1 egg, room temperature, beaten
1 teaspoon pure vanilla extract
1/4 cup blackberry jam

Directions:
Put an oven rack in the center of the oven. Preheat the oven to 375 degrees F. Line 2 baking sheets with parchment paper. Set aside.
In a medium bowl, sieve together the flour, cocoa powder, baking soda, and salt. Set aside.
In a stand mixer, fitted with the paddle attachment, beat the butter, peanut butter, 3/4 cup of sugar, and light brown sugar together, scraping down the sides of the bowl as needed, until smooth, about 30 seconds. Add the egg and vanilla extract and mix until blended. With the machine running on low speed, gradually add the flour mixture until incorporated.
Put the remaining 1/4 cup of sugar in a small bowl. Form the dough into 1/4 cup-size balls and roll in the sugar. Arrange 5 balls of dough, evenly apart, on each baking sheet. Using a round 1/4 teaspoon measure, or the thin end of a wooden spoon, make a hole in the center of each ball of dough, about 1/2 to 3/4-inch deep. Spoon 1 teaspoon of jam into each hole. Bake for 11 to 14 minutes until the dough has spread and the surface of the cookies are crackled. Cool for 5 minutes and transfer to a wire rack to cool completely, about 20 minutes. Arrange the cookies on a serving dish and serve.