- Using electric beaters or a stand mixer fitted with the paddle attachment, beat the butter on medium speed for 1 minute, until fluffy. Add the icing sugar and vanilla and mix, starting on low and increasing to medium, for 1 minute.
- Sift in the flour, cornstarch and salt, add the cornmeal, and mix on medium-low speed until the dough comes together. Shape into a disc, wrap in plastic wrap and chill for at least 2 hours before rolling.
- Preheat the oven to 325°F (160°C) and line 2 baking trays with parchment paper.
- On a lightly floured surface, knead the dough just a little to soften it (this will prevent cracking as you roll). If you find the dough cracks as you begin to roll it, gather it up and knead again to soften it further. Roll into a circle just under 1/4 inch (6 mm) thick. Use a 2 1/2-inch (6.5 cm) fluted round cookie cutter to cut out cookies and re-roll any scraps as needed (it re-rolls nicely).
- In the centre of each cookie, drop about ¾ tsp of raspberry jam and a spoonful of apricot, side by side. Hold 2 opposite edges of the dough in your hands and bring them together over the jam. Pinch them to seal, ensuring that some raspberry jam peeks out of one side and some apricot jam peeks out the other. Place the cookies on the tray, 1 1/2 inches (3.5 cm) apart.
- Brush the cookies with the egg white and then sprinkle with cinnamon sugar.
- Bake for 15 to 18 minutes, until golden at the edges. Let cool completely on the tray on a wire rack.
Make Ahead Tip: You can store these baked cookies for 1 week in an airtight container at room temperature. As a rule, jam-filled cookies become soft and fragile if frozen and then thawed. To get ahead, make the dough and freeze it, shaped into a disc and well wrapped, for up to 3 months. To bake, thaw the dough overnight in the fridge before rolling, cutting, filling and putting the cookies in the oven.
From Set for the Holidays with Anna Olson, Appetite by Random House, 2018.