Preheat the oven to 425F. Line a standard 12-cup muffin pan with 6 muffin liners, meaning you'll only fill every other muffin well with batter. OR line a 6-cup jumbo muffin pan with 3 liners. Set aside.

In a medium bowl, use a handheld electric mixer to beat the cream cheese to smooth. Then beat in sugar, vanilla, and salt for about 2 minutes, until very smooth and creamy. Transfer the cream cheese filling to a piping bag or a large ziplock bag. Set aside.

In a medium bowl, mix together the flour, sugar, cinnamon, and salt. Then add in the melted butter and vanilla, and use a fork to mix together until it forms a crumble and resembles wet sand. Cover the bowl and place into the refrigerator until ready to use.

Prepare the blueberry muffin batter. In a large bowl, whisk together the flour, baking powder, baking soda, salt, and cinnamon. Set aside.

In a separate large bowl whisk together the melted butter, oil, sugar, and eggs until well combined.

Then, add the buttermilk, Greek yogurt or sour cream, and vanilla. Whisk until well combined and the mixture is a pale yellow.

Add the dry ingredients to the wet, and use a spatula or wooden spoon to fold together, until just barely combined and there are no flour streaks (the batter will be thick).

In a small bowl, toss the blueberries with 1 1/2 tbsp (12g) of all-purpose flour. Then fold the blueberries into the batter until evenly dispersed.

Scoop and divide the batter among the prepared muffin cups, filling them to the rim.

If desired and using, place ~1 tsp of blueberry preserves on top of the muffin batter for each muffin.

Snip the tip off of the piping bag with the cream cheese filling (or the corner of the ziplock bag), and place it into the center of the batter for each muffin, pushing it about halfway down. Press down to squeeze, pulling up slowly in a circular motion to make a little swirl at the top to fill out a small circle at the surface of the batter, so the cream cheese is exposed. All of the filling should be used!

Then, sprinkle the crumb topping on top of the muffins, placing it around the cream cheese, not over it.

For regular-sized muffins: bake at 425F for 5 minutes. Then keeping the muffins in the oven, reduce the oven temperature to 350F and continue to bake for another 15-20 minutes, until the tops are lightly golden and a toothpick inserted into the middle comes out clean or with moist crumbs.

For jumbo muffins: bake at 425F for 5 minutes. Then turn the oven temperature down to 350F and bake for another 25-30 minutes, until the tops are lightly golden and a toothpick inserted into the middle comes out clean or with moist crumbs.

Remove the muffins from the oven and allow them to cool in the pan for 5 minutes. Then remove them from the pan and transfer to a wire cooling rack.

Serve the muffins warm with a hot cup of coffee.

Enjoy!