Make a double boiler by simmering 3" deep of water in a large saucepan. In a medium/large stainless steel bowl, whisk together eggs, yolks, and sugar until sugar just starts to dissolve.
Whisk in both juices and zest.
Set bowl over saucepan of simmering water. Cook curd, stirring with a rubber spatula almost constantly, until it begins to thicken. It should have the consistency of loosely whipped cream. Remove from heat.
Stir in butter cubes all at once, stirring until butter is completely melted and fully incorporated. Strain through a fine mesh strainer to remove bits of zest and any solid egg proteins.
Chill at 2 hours before using in the cookies. This makes about 1 ¾ cups-- you will only use about ½ cup for the cookies. Store the rest for another purpose.
For the Vanilla Pinkprint Cookie Dough
Line two baking sheets with parchment or non-stick mats.
Using an electric mixer, beat the butter, sugar, and salt on medium-high until light and fluffy, 2 - 3 minutes.
Beat in the egg and vanilla until fully incorporated and fluffy. On low speed, blend in the flour until just incorporated.
Using small scoop, scoop up a bit of dough and roll into a 1" ball with your palms. Place on the baking sheet. Using your pinky, press down near the top of the ball, making an indentation. Make another indentation right next to it. Make a third indentation centered in the hollow just below the first and second indentations to begin making a heart shape in the dough. Use your fingers to elongate the edge at bottom of the ball, and to make a dent in the edge of the top of the ball. Repeat, making fun little heart shapes, each with their own personality, using up the dough. You should have close to 20 hearts on each baking sheet.
Chill dough hearts until they are very firm, at least an hour. This part is critical, or you'll end up with a puddle in the end.
Putting the cookies all together:
Preheat oven to 350°. Bake one sheet for 7 minutes. Working quickly, once again use your pinky to depress the heart shape that has puffed up. It will be hot, so use caution. Using a very small spoon, like a baby or demitasse spoon, fill the depressions with cold blood orange curd. Don't over flow! Place the cookies back in the oven for another 5 - 7 minutes, keeping a close eye. You want them fully cooked and just barely beginning to go golden on the bottom, but not browning on the cookie itself. Allow to cook for two or three minutes on the baking sheet, to set up, them remove to a cooling rack to complete cooling. Store in an airtight container for up to a week, if they last that long.
Make It Your Own:Use store- bought lemon, lime, or raspberry curd instead of making your own. Easier yet, fill them with any red or pink jam.Save time by simply using your thumb to make an indent. No need to make a heart to make these cookies pretty and delish all year long.