Warm the heavy whipping cream in a medium sauce pan until warm, add in the cinnamon and vanilla extract. Whisk to combine. Allow to infuse for 5-10 minutes.
Add the chopped white chocolate into a large mixing bowl or into the bowl of a stand mixer. Pour the warm cinnamon cream mixture over the white chocolate and stir gently as the chocolate starts the melt. The cream should completely melt the chocolate, stir until you have a smooth mixture. It will still be very runny.
Cover with plastic wrap and allow to set in the fridge overnight or for at least 3-4 hours.
After the ganache has set and cooled completely, use a stand or hand mixer fitted with a whisk attachment and whip for 4-6 minutes until stiff. After a few minutes of whipping check the consistency of the ganache, you want a stiff frosting that will hold its shape.
Once the whipped ganache is done it will be thick and much lighter in color. Transfer to a piping bag fitted with a tip of choice. You can also spread the frosting between the cookies with a knife. If you plan to make the frosting ahead of time keep chilled until an hour before you plan to use it, allow to come to room temperature before piping.
For the Snickerdoodle Cookies:
Preheat oven to 350 degrees F. Line a couple cookie sheets with parchment paper and set aside.
In a large mixing bowl, cream butter and sugar for 4-5 minutes until light and fluffy. Scrape the sides of the bowl and add the eggs and vanilla. Cream for 1-2 minutes longer.
In a small mixing bowl combine the flour, cream of tartar, baking soda, and salt. With the mixer on low slowly add in the dry ingredients and mi until fully incorporated. Scraping down the sides as needed.
Chill the dough for 25-30 minutes, or overnight if needed. If chilling overnight, allow the dough to come to room temperature before scooping. Using a measuring spoon or a cookie scoop, scoop out even amounts of dough, about 1 1/2 tablespoons. Roll into small balls until round and smooth. Repeat until all of the dough has been used.
In a small mixing bowl combine the white sugar, brown sugar, and cinnamon. Stir to combine. Roll each cookie into the sugar mixture and coat well. Arrange 2 inches apart on the prepared cookie sheets, baking in batches if needed. **The cookies will flatten out pretty well on their own, but if you desire a flatter cookie for your sandwich, gently press down on the center of the dough.
Bake for 9-11 minutes until slightly golden brown, the cookies will still be very soft. Allow to cool 3-5 minutes on the cookie sheet before transferring to a cooling rack. Repeat with remaining cookies. Allow cookies to cool completely before adding frosting.
Pipe or spread the whipped ganache frosting between two cooled snickerdoodles, set aside finished sandwich cookie and repeat with remaining. These are best enjoy the same day, but will keep for 2-3 days in the fridge if stored in an airtight container.
Notes
**Snickerdoodle dough can be made up to a day in advance. If making in advance, I recommend scooping your cookies and arranging them in a single layer on a baking sheet prior to chilling. This way the are ready to bake when desired, just allow to come to room temperature slightly before baking.**I don't flatten my cookies when baking, if you want a flatter cookie for your sandwich, gently press the middle of the cookie dough to flatten slightly. If you chose to flatten the cookies - you most likely will need to shorten the baking time.**You can also infuse your cream with cinnamon sticks rather than ground cinnamon - this will take longer to infuse he cinnamon flavor. I personally like how the ground cinnamon leaves little specks!