In a small bowl, mix together 2 tablespoons of granulated sugar, 2 tablespoons of brown sugar, 1 teaspoon of ground cinnamon, 1 teaspoon of salt, and 1 cup of all-purpose flour. Pour in the melted butter and stir until the mixture resembles coarse crumbs. Set aside.
Preheat your oven to 350°F (175°C). This step is crucial for ensuring your cake bakes evenly.
In a large mixing bowl, cream together 1 cup of room temperature unsalted butter and 1 cup of granulated sugar until light and fluffy. This will take about 2-3 minutes with an electric mixer.
Add in the 2 eggs and 1 teaspoon of vanilla extract to the butter-sugar mixture. Beat until well combined.
Mix in 1 cup of Greek yogurt until the batter is smooth. The yogurt will add moisture and richness to the cake.
In a separate bowl, whisk together 2 cups of all-purpose flour, 2 teaspoons of baking powder, 1 teaspoon of baking soda, and 1 teaspoon of salt. Gradually add this dry mixture to the wet ingredients, mixing until just combined.
Gently fold in 1 cup of semi-sweet chocolate chips, 1 cup of peanut butter chips, and 1 cup of mini milk chocolate chips into the batter.
Pour half of the batter into your prepared baking dish. Sprinkle half of the crumb topping over this layer. Then, pour the remaining batter over the crumbs and finish with the rest of the crumb topping.
Place the baking dish in the preheated oven and bake for 35-40 minutes or until a toothpick inserted into the center comes out clean.
Once baked, remove the cake from the oven and let it cool in the pan for about 10 minutes. Then transfer it to a cooling rack. After it’s completely cooled, dust the top with powdered sugar for a beautiful finish.