Preheat oven to 325 F. Line a 8×8 inch baking dish with parchment paper.
In a bowl, combine cookie crumbs and melted butter. Press mixture to the bottom of the baking dish. Bake crust for 8 minutes, then cool completely.
Reduce oven temperature to 300F.
FOR THE CHEESECAKE:
In the bowl of a stand mixer, fitted with paddle attachment beat cream cheese for 3 minutes. Scrape the sides of the bowl. Add sugar and flour and beat for 2 more minutes. Scrape down the sides of the bowl.
Add eggs one at a time, beating to incorporate after each addition.
Add sour cream/Greek yogurt and mix until just combined. Add vanilla and mix to combine.
Pour batter over the cooled crust and bake for 50-55 minutes, until the top is set and starting to lightly brown.
Turn the oven off and let the cheesecake cool down for 20 minutes inside. Remove from the oven and cool at room temperature, then refrigerate for at least 2 hours, before you add the mousse layer.
FOR THE PEAR MOUSSE:
Peel, core and chop pears. Combine pears, sugar, butter, cinnamon and lemon juice in a pan. Cook on low heat for 15 minutes, stirring frequently. Cool for 20 minutes. Place in a blender and puree until smooth. Cool in the fridge for 30 minutes.
Beat heavy cream until stiff peaks form.
In a small bowl, sprinkle gelatin over cold water. Let it sit for 5 minutes, then place over double boiler or in the microwave for 30 seconds to melt and liquify.
Add pear puree to whipped cream, mix until just combined. Add gelatine/water mixture and mix for 1 minute.
Spread mousse mixture over cooled cheesecake. Use a spatula to make the top smooth.
Refrigerate for at least 1 hour.
Slice cheesecake into 9 squares. Top with pear slices to decorate. Sprinkle with cinnamon.
Optional: Add 1 drop orange food coloring to the mousse to make it more yellow if you'd like.