Make the raspberry puree

1. Heat 1 cup of the berries over medium heat in a small pan.  Once the berries have defrosted, simmer for 5 minutes.  Take the raspberries off the heat and press the berries through a fine mesh sieve

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   to strain out the seeds.  You should have 3 Tablespoons of raspberry puree.
2. Whisk the oil together with the vanilla and the raspberry puree.

Make the raspberry cookie dough

1. Beat the butter in a stand mixer or with a hand mixer just to soften it.  Slowly drizzle in the oil with the mixer on until you have a smooth mixture of butter and oil.
2. Add in the sugars and beat to combine.
3. Mix in the egg.  Scrape down the sides of the bowl, and then mix for a few more seconds until you have a very smooth batter.
4. Whisk the flour, baking soda, cream of tartar and salt in another bowl.
5. Add the flour and the rest of the raspberries to the mixer, and then beat until the flour just disappears.  If you’re using mini chocolate chips instead of the chocolate hearts, mix them in at this point too.
6. Chill the dough in the refrigerator for 30 minutes.

Make the cookies

1. Pour the powdered sugar for rolling into a pie plate

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   or other shallow tray.  Scoop out balls of dough with a cookie scoop or using a spoon.  Roll the dough balls in the powdered sugar.
2. Place the sugared dough balls in a tray and chill for 15 minutes.
3. Preheat the oven to 350 F (180 C).  Line 2 sheet trays with parchment

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   .

Baking and finishing

1. While the oven is heating up, take out the cold dough balls.  Roll them in your hands to round off the shape, and then roll them again in powdered sugar.
2. Place 8 balls on a sheet tray for baking.
3. Loading up the oven with 2 sheet trays at a time, bake the cookies for 5 minutes.  After 5 minutes, rotate the sheet trays 180 degrees, and then swap the trays from top to bottom (or bottom to top as it were).  Bake for 5 more minutes (10 minutes total).
4. After 10 minutes, place a chocolate heart in the center of each cookie.  Place the cookies back in the oven to bake for 2 more minutes.
5. Allow the cookies to cool for about 5 minutes before moving them to a cooling rack to finish cooling.  If you want to transport the cookies, you’ll need to wait until the chocolate hearts re-solidify.  You can speed up this process by chilling the finished cookies. 
6. Store the cookies in an airtight container at room temperature for up to 1 week.