Start by preheating your oven to 350°F (175°C) so it’s hot when the batter is ready. While the oven heats, grease your 9x13-inch baking dish or springform pan with butter or cooking spray. This helps stop the cake from sticking and makes it easy to take out after baking.

Take a large mixing bowl and combine your dry ingredients—flour, baking powder, baking soda, and a pinch of salt. Gently whisk everything together to ensure even distribution. A well-mixed dry base ensures the perfect texture and balance of flavors in your coffee cake.

Next, in a medium mixing bowl, use your hand or stand mixer to cream together the butter and sugar until the mixture becomes light and fluffy. This process helps incorporate air, giving the cake its tender and moist crumb. Take your time with this step to achieve the best results.

Start adding the wet ingredients by cracking in the eggs, one at a time, into the creamed butter and sugar. Give it a good mix after each one. Next, stir in the vanilla extract and sour cream. The sour cream brings a nice tangy flavor and keeps the cake super moist and delicious!

Gradually add the dry ingredients to the wet mixture in batches. Use a rubber spatula to fold them together gently to avoid overmixing. The batter should be thick yet smooth, perfect for creating a coffee cake that’s light and fluffy but holds its structure beautifully.

For the irresistible crumble topping, combine sugar, flour, cinnamon, and cold butter in another bowl. Use a fork or pastry cutter to blend everything until the mixture forms coarse crumbs. If desired, toss in some finely chopped walnuts or pecans for added crunch and flavor.

Pour half of the batter into the prepared pan, spreading it evenly with the spatula. Sprinkle half of the crumble topping over this layer, ensuring it’s distributed edge to edge. Pour the remaining batter on top and gently even it out. Finish with the rest of the crumble topping for a fantastic textured crust.

Place your assembled coffee cake into the preheated oven and bake for 30-35 minutes, or until a toothpick inserted into the center comes out clean. The topping should be crisp and golden while the inside remains soft and tender.

Once baked, remove the cake from the oven and allow it to cool in the pan for about 10-15 minutes. If you’re using a springform pan, carefully release the edges. Serve warm or at room temperature, perhaps with a dusting of powdered sugar or alongside a freshly brewed cup of coffee. Enjoy the comforting flavors of Grandma’s secret New England Coffee Cake!