For the dough:
14 tablespoons (1 and 3/4 sticks) unsalted butter, at room temperature
1 cup confectioners' sugar
2 large egg yolks, at room temperature
1 teaspoon vanilla extract or vanilla bean paste
1 cup cake flour, measured using the spoon and level method
1 cup + 2 tablespoons all purpose flour, measured using the spoon and level method
For the filling:
4 tablespoons (1/2 stick) unsalted butter, at room temperature
4 tablespoons (1/4 cup) vegetable shortening
2 cups confectioners' sugar, sifted before measuring
2 teaspoons vanilla extract or vanilla bean paste
1. In a In the bowl of a stand mixer fitted with the paddle attachment, beat the butter, confectioners' sugar and egg yolks until light and creamy, about 3 minutes. Add the vanilla and beat until incorporated.
2. In a medium bowl, whisk together the flours. Add to the butter mixture and beat until combined, about 30 seconds. Scrape the dough from the mixer bowl onto a piece of plastic wrap and form into a disc. Wrap tightly and chill in the refrigerator for at least an hour and up to two days. (The dough may be frozen for up to a month. Defrost in the plastic wrap to allow condensation to collect on the plastic and not the dough.)
3. When you're ready to bake the cookies, heat the oven to 325 degrees F. Remove the dough from the plastic wrap and roll out on a lightly floured surface to a scant 1/4 inch thickness. Cut cookies with a 2-inch round biscuit or cookie cutter. Use a heart-shaped mini cutter to cut hearts out of half the cookie rounds.
4. Transfer cookies to a parchment- or silicone-lined baking sheet and bake for 15 to 20 minutes or until lightly golden, rotating the sheets halfway through baking. Allow to cool completely before filling and assembling.
5. To make the cream filling, beat together the butter, shortening, sugar and vanilla until light and fluffy, about 3 minutes.
6. To assemble the cookies, use an offset spatula to spread the cream filling on the underside of the cookies that don't have hearts cut out of them. The cream filling should be about 1/4 inch thick and not quite reach the edges of the cookies. Top each cookie with a layer of strawberry jam and a heart cutout cookie.