Add the sugar and butter to a large mixing bowl (or use a standing mixer). Use an electric mixer to beat on high speed until light and fluffy, 3-4 minutes.
Add the egg and vanilla and beat again for a minute, or until very fluffy and with a slightly stiffer consistency.
Add the flour, hazelnut meal, orange zest, and salt. Mix on low speed until a crumbly dough forms. It looks dry but isn’t.
Separate the dough into two equal halves. Use your hands to press one half into a rough disc and place it onto a large sheet of parchment paper.
Place another sheet of paper over the dough, and roll out to about 25×35 cm (10×14 inches). Repeat with the second half of dough, then slide them onto baking sheets and chill for about half an hour in the refrigerator.
Preheat the oven to 350°F (180°C). Once the dough has chilled, cut the cookies into small rounds (or fluted rounds as pictured), about 4 cm (1.5 inches) across.
For the second half of the cookie dough, cut the cookies in the same shape, then use the large end of a piping tip to cut small circles in the middle of each.
Bake the cookies for 8-10 minutes, or until the edges are lightly golden. Cool on the pan for 5 minutes before removing carefully and cooling fully on a wire rack.
Once the cookies are cool, add the jam filling. Place about a half teaspoon of jam onto each full cookie base, then top with the cookies that have holes cut into them, to allow the jam to peek through.
Top the cookies with a generous dusting of icing sugar. The sugar will dissolve where it hits the jam. Store the cookies for up to a week in an airtight container, or freeze up to a month.
Notes
• We used plum jam, but raspberry is classic and would be good here.