• Preheat the oven to 350°F. Line a 9-inch springform pan with parchment paper and spray the side with a baking spray. You can also use a medium-sized square pan, if desired.

Preparing the Cake Batter:

• Place the sugar, eggs, and vanilla extract into large mixing bowl. Using a mixer, beat the eggs and sugar together for 3 to 4 minutes, until fluffy.
• Next, add the sour cream or Greek yogurt and mix again until well combined; about 1 minute. Pour in the oil and mix briefly, just until combined.
• In a separate mixing bowl, combine the dry ingredients: all-purpose flour, baking soda, baking powder, sea salt, cinnamon, and nutmeg.
• Sift the dry ingredients into the wet batter. Use a mixer to combine everything together, mixing for a few minutes until the batter is smooth and clump free.
• In a separate bowl, combine the blueberries with the cornstarch. Toss the berries until they’re well coated, then fold them into the batter.

Making Oat Crumble:

• In a small bowl, combine the rolled oats, diced nuts, brown sugar, cinnamon, and flour.
• Use a coarse cheese grater and grate in the frozen butter. Use your finger to combine all the ingredients together.

Baking Instructions:

• Transfer the prepared cake batter into your lined baking pan. Use a spatula to spread the batter evenly, making sure it’s flat on top.
• Sprinkle the oat crumble over the top in an even layer.
• Bake the cake at 350°F for 65 to 80 minutes, or until a toothpick inserted into the center comes out clean.
• Remove the cake from the oven, let it sit in the pan for 5 minutes, then carefully remove it from the pan and onto a wire cooling rack to cool.

Making Blueberry Whipped Cream:

• For the whipped cream – pour chilled heavy cream into a large mixing bowl and add the powdered sugar, vanilla extract, and sea salt.
• Using a mixer, whisk for 3 to 5 minutes until stiff peaks form.
• Add the blueberry preserves last and whisk again for about 30 seconds, until well incorporated.
• Transfer the whipped cream into a pastry bag tipped with a star tip, or simply spoon it onto each slice of cake.

Serving & Storing:

• I personally love to enjoy this blueberry cake while it’s still warm with a large dollop of blueberry whipped cream on the side. It’s fantastic with a cup of coffee or tea, too!
• Store the cake at room temperature for up to 2 days. For longer storage, allow the cake to cool down first, wrap it in plastic wrap, and refrigerate. Keep the whipped cream separately.