Add flour and instant yeast to one side of a large bowl. Add sugar and salt to the opposite side. This keeps the salt from killing the yeast before mixing.

Pour in warm milk, eggs, melted butter, banana extract, and vanilla extract. Stir with a wooden spoon or dough whisk until a shaggy dough forms.

Transfer to a stand mixer with dough hook. Kneading|Knead 6-8 minutes on medium speed until smooth, elastic, and slightly tacky. By hand, this takes 8-10 minutes.

Stretch a small piece of dough using the windowpane test. It should stretch thin enough to see light through without tearing. If it tears, knead another 2 minutes.

Coat a large bowl with softened butter.

Form the dough into a smooth ball and place seam-side down in the bowl.

Cover with plastic wrap or a damp towel. Let rise at room temperature (75-78°F) until doubled, about 60-90 minutes.

Add walnuts to a dry skillet over medium heat. Stir frequently for 3-4 minutes until fragrant and lightly golden. The Maillard reaction transforms them. Transfer to a plate to cool, then roughly chop.

In a small bowl, combine brown sugar, cinnamon, salt, lemon zest, and 2 drops of vanilla extract. Mix well.

If using fresh berries, toss them with cornstarch in a small bowl. This prevents bleeding and sliding. If using frozen, do not thaw. Add them straight from the freezer.

Make sure the 85g of butter for the filling is very soft, almost spreadable like mayonnaise.

Gently deflate the dough. On a lightly floured surface, roll into a 16x20-inch rectangle, about ¼-inch thick.

Using an offset spatula or the back of a spoon, spread the softened butter edge to edge. Don't leave bare spots.

Dollop blueberry preserves in small spoonfuls across the butter. Use the back of the spoon to swipe it around. It doesn't need to be perfectly even.

Distribute the cinnamon sugar mixture evenly over the entire surface.

Scatter the cornstarch-coated blueberries and toasted walnuts evenly across the dough.

Starting from the long edge closest to you, roll the dough away from you into a tight log. Use both hands and keep even pressure. When you reach the bare edge, pinch the seam to seal.

Cut off about 1 inch from each end. These pieces are uneven and can be baked separately as baker's treats.

Using a sharp knife or unflavored dental floss, cut the log into 9 equal pieces, about 2 inches each.

Butter a 9x13-inch baking pan. Place larger rolls around the edges (where they get more heat) and smaller ones in the center. Leave a little space between each roll.

Loosely cover with plastic wrap or a clean kitchen towel.

Let rise at room temperature for 45-75 minutes. Rolls should look puffy and have expanded to nearly touch each other.

Cover tightly and refrigerate overnight (8-12 hours). In the morning, remove from fridge and let sit at room temperature for 30-45 minutes before baking.

Heat to 350°F (175°C). Position rack in center.

Just before baking, brush the tops of the rolls with heavy cream. This promotes browning and adds richness.

Bake 28-35 minutes until the tops are golden brown and the internal temperature reaches 190°F (88°C).

Let rolls cool in the pan for 10 minutes before frosting. This lets them set but stay warm enough to melt the frosting slightly.

In a medium bowl, beat softened cream cheese and butter together until smooth, about 2 minutes.

Sift in powdered sugar. Beat on low until combined, then increase speed and beat until fluffy.

Add 2 tablespoons heavy cream and vanilla (or banana) extract. Beat until smooth. Add more cream if needed for spreading consistency.

Dollop 2 teaspoons of blueberry preserves on top. Use a knife or toothpick to gently swirl. Do not overmix. You want visible purple streaks, not uniform color.

Spread or dollop the swirled frosting over the warm rolls. Let some melt into the crevices.

These are best eaten warm. Leftovers can be stored covered at room temperature for 2 days or refrigerated for up to 5 days. Reheat in microwave for 15-20 seconds.

Cut the log into 9 equal pieces. Place larger rolls around the edges and smaller ones in the center.

Cut the log into 12 smaller pieces for individual servings with crispier edges.

Preheat oven to 350°F (175°C).

Brush rolls with heavy cream for shine and browning.

Bake 28-35 minutes until golden.

Internal temp should reach 190°F (88°C).

Let cool 10 minutes before frosting.

Butter skillet generously.

Arrange 9 rolls in skillet and proof as directed.

Bake at 350°F for 30-38 minutes (cast iron holds more heat).

Internal temp should reach 190°F. Let cool in skillet 10 minutes.