Upside down Blackberry Cake

originally found at digestivediva.blogspot.com
2 1/2 cups fresh blackberries (12 oz)
1/2 cup plus
1 1/2 tablespoons sugar
1 cup plus 1 teaspoon Pamela's Pancake and Baking Mix
1/2 stick (1/4 cup) unsalted butter, softened
1 large egg
1 teaspoon vanilla
1/2 cup well-shaken buttermilk
Preheat oven to 400 F.Line bottom of a buttered 8- by 2-inch round cake pan with 2 rounds of parchment paper, then butter parchment. Dust pan with some flour, knocking out excess.Arrange blackberries in 1 layer in cake pan. Sprinkle berries with 11/2 tablespoons sugar and shake pan to help distribute sugar.Beat together butter and remaining 1/2 cup sugar in a large bowl with an electric mixer at high speed until light and fluffy, about 2 minutes. Add egg and vanilla and mix at low speed until just incorporated. Alternately add baking mix and buttermilk in 3 batches, mixing at low speed until just incorporated.Spoon batter evenly over berries, smoothing top, and bake in middle of oven until top is golden and a tester comes out clean, 30 to 35 minutes (mine took 45 min).Run a thin knife around edge of pan, then invert a large plate over pan and, using pot holders to hold plate and pan together tightly, flip cake onto plate. Peel off parchment and serve cake with ice cream.