Preheat the oven to 350°F. Grease a nine-inch cake pan and line the bottom with parchment paper.
Add the one-half cup of butter and three-quarter cups of white sugar to the bowl of your stand mixer. Beat until the mixture is fluffy, about five minutes.
Add two egg and one teaspoon of vanilla extract beat at medium speed until the mixture is smooth. Don’t forget to scrape down the sides of the bowl using a spatula to make sure everything is incorporated.
Add one-half cup of milk and one-half cup of sour cream and beat on low speed until combined.
Alternately, add two cups of Bisquick into the bowl of the stand mixer with the wet ingredients. Turn the mixer on low and mix just until the batter comes together.
Over-mixing can cause a dense cake, which you don't want.
Using a rubber spatula, scrape down the sides of the bowl once again.
Transfer the batter into the pan, using a spatula to disperse.
Spread the sliced pears over the top of the batter.
To make the streusel topping, mix two-thirds of a cup of Bisquick, two-thirds of a cup of white sugar, and one-half teaspoon of cinnamon. Add four tablespoons of melted butter and mix with a fork until the mixture becomes crumbly.
Sprinkle the streusel mixture over the cake and the pears, spreading it at evenly as possible and into all the corners.
Bake the cake for sixty minutes or until the top is lightly browned on top. Check for doneness by inserting a toothpick into the center of the cake. If the toothpick comes out clean, then the cake is done.
Allow the cake to cool in the pan for at least twenty minutes before cutting into it.
Serve and enjoy!