1/2 cup (113 grams) unsalted butter, room temperature
1/4 cup (50 grams) granulated white sugar
1 large egg, separated
1/2 teaspoon pure vanilla extract
1 cup (130 grams) all purpose flour
1/8 teaspoon salt
3/4 cup (80 grams) hazelnuts, almonds, pecans or walnuts, toasted and finely chopped (See Note)
1/4 - 1/2 cup (60 - 120 ml) raspberry jam
Thumbprint Cookies: In the bowl of your electric mixer (or with a hand mixer), beat the butter and sugar until light and fluffy (2-3 minutes). Add the egg yolk and vanilla extract and beat until combined.
In a separate bowl, whisk together the flour and salt. Add the flour mixture to the batter and beat just until combined. If the batter is too soft to roll into balls, refrigerate for about 30-60 minutes.
Preheat oven to 350 degrees F (177 degrees C) and place rack in center of oven. Line a baking sheet with parchment paper.
In a small bowl, whisk the egg white until frothy. Place the finely chopped nuts on a plate. Roll the dough into 1 inch (2.5 cm) balls. Taking one ball of dough at a time, dip first into the egg white and then lightly roll in the nuts. Place on the prepared baking sheet spacing about 1 inch (2.5 cm) apart. Using your thumb or end of a wooden spoon, make a indentation into the center of each cookie and fill with about 1/2 teaspoon of jam.
Bake for about 12 - 15 minutes, or until cookies are set and the nuts have nicely browned. Remove from oven and place on wire rack to cool.
Note: To toast the nuts. Spread nuts on a baking sheet and bake in a 350 degree F (180 degree C) oven for 8-10 minutes (almonds, pecans and walnuts). The nuts are done when they are light golden-brown in color and fragrant. Toast the hazelnuts for about 15 minutes or until fragrant and the outer skins begin to flake. Remove from oven and place the hot nuts in a dish towel. Roll up the towel and let the nuts sit (steam) for a few minutes then rub the nuts in the towel briskly to remove the skins. Let cool completely. Once the nuts have cooled, place them in your food processor and process until finely chopped. Alternatively, you could chop them by hand.
Note: If you are planning to store these cookies for more than a couple of days, I like to bake them without the jam. Just reduce the baking time by a few minutes. These cookies can be stored for about a week. Fill the cookies will jam the same day as serving.
Makes about 20 cookies.
Thumbprint Cookies are a very popular holiday cookie. They are made with a shortbread-like dough that is formed into balls and then rolled in either finely chopped nuts or dried coconut. The name 'thumbprint' comes from the fact you use your "thumb" to make an indentation into each ball of dough and then fill it with jam.
Once the Thumbprint Cookie dough is made, if it is too soft to roll into balls, cover and refrigerate until firm. This can take anywhere from 30 minutes to a couple of hours. Then roll the dough into one inch (2.5 cm) balls, and try to make all the cookie balls the same size so they bake evenly. Then each ball of cookie dough is rolled, first in a beaten egg white and then in finely chopped nuts. You can use a variety of nuts to cover the balls of dough; hazelnuts, pecans, almonds or walnuts are all excellent choices. Toasting the nuts first brings out their flavor and once they have cooled, they are finely chopped. Next, using your thumb or the end of a wooden spoon, make a indentation into the center of each cookie. Fill the indentation with about 1/2 teaspoon of your favorite jam. Now, some recipes do call for filling the centers of the cookies with jam after they are baked. This is best if you want to store the cookies for more than a few days as the jam will soften the cookies over time.
Although I have filled the cookies with raspberry jam, feel free to use any flavored jam you like. I do like to use a sweet yet tart flavored jam (like raspberry), as I like how it offsets the sweetness and richness of the cookie. If you decide to use preserves, just make sure to strain the preserves first to remove any large pieces of fruit. (Note: Jam and preserves are similar in that they are both a cooked combination of fruit and sugar (and sometimes pectin). The difference being that preserves still contain chunks of fruit, whereas jam is more like a smooth fruit puree.)