For the Crust:
Preheat oven to 350 degrees. Lightly grease a tart pan with non stick spray, set aside.
Prepare the crust: crush graham crackers in a food processor or in a plastic bag with a kitchen mallet until they are fine crumbs. Pour the crumbs into a bowl, add ground cinnamon to the crumbs. Give the crumbs a quick stir to mix in the cinnamon. Melt the butter in a small sauce pan on the stove top over low-medium heat. You want to brown the butter so allow the butter to foam and bubble, stirring it every so often, but don’t leave it unattended. When the butter stops bubbling and has a nutty aroma stir it consistently until it turns a amber color and immediately take it off the heat. Brown butter can burn quickly so once it turns that beautiful amber shade take it off the heat. Give it another stir and pour it in a small bowl and allow it to cool for a few minutes. Then add the butter to the graham cracker crumbs and mix everything together, crumbs should be thoroughly coated and moist. Pour the crumb/butter mixture into the tart part and firmly pack it together to form a crust, make sure to fill all the ridges on the sides.
Bake the crust for 7 to 8 minutes in the oven.
Prepare the chocolate ganache: Add the chocolate chips to a heat safe mixing bowl. Pour the heavy cream, butter and espresso powder to a small sauce pan over low medium heat on the stove, letting it comes to a soft boil, stirring frequently so the cream doesn’t burn. Once the heavy cream start to bubble take it off the heat and pour the mixture right over the chocolate chips. Let everything sit for 2 to 3 minutes. Then, stir the ingredients together until the chocolate chips are completely melted and a smooth, shiny ganache forms. Pour the ganache right into the tart pan and smooth out the top if necessary. Place the tart pan in the refrigerator for the filling to firm up and set, for at least 4 to 6 hours but preferably overnight.
Making the meringue topping: Place the egg whites and cream of tartar in a glass mixing bowl. Using a hand held electric mixer or a stand mixer with a fitted whisk attachment beat the egg whites on medium high speed. Once the egg whites start to have a fluffy texture and are white, slowly add in the sugar, a little at a time, with the mixer still on. Continue beating the egg whites until stiff peaks form. Meringue should be firm enough that it will hold it’s shape but is still spreadable and have a super white, shiny appearance. Now you have a few options: you can either spoon the meringue over the entire top of the tart, or you can transfer it into a piping bag with a tip of your choice and pipe various swirls and designs on the tops. It’s totally up to you! Use a small kitchen torch to toast the meringue to your preference. Tart can be sliced and served immediately. Store and leftover in the refrigerator.