Method:
Preheat oven to 350°F. Generously grease a 9-inch round cake pan. Cut a piece of parchment paper to fit the bottom of the pan then use it to line the pan; set aside. In a small bowl, stir together heavy cream and sugar until combined. Spread mixture evenly over bottom of pan; set aside.
Melt butter in a large skillet over medium high heat. Arrange pears in skillet in a single layer and cook, flipping once, until edges are deep golden brown, 2 to 3 minutes per side. Remove from heat and set pears aside to let cool slightly. Arrange pears in the bottom of the pan in a decorative pattern then sprinkle with walnuts.
In a medium bowl, prepare cake mix according to package directions. Pour batter over pears and smooth out with the back of a spoon. Bake until a toothpick inserted into the center comes out clean, 40 to 45 minutes. Transfer pan to rack to let cool then run a knife around edge of cake to release it from pan. Invert cake onto a plate, remove and discard parchment paper, cut cake into slices and serve.