Step 1: In a large mixing bowl, combine the warm milk, melted butter, and granulated sugar. Sprinkle the instant yeast over the top and let it sit undisturbed for about 5 minutes. You'll see a frothy layer form, which tells you the yeast is active and ready to work its magic.
Step 2: In a separate, medium-sized bowl, whisk together the all-purpose flour and salt until they are thoroughly combined.
Step 3: Gradually add the dry flour mixture to the wet yeast mixture, stirring until a shaggy dough begins to form. Incorporate the eggs one at a time, mixing until fully absorbed. Then, turn the dough out onto a lightly floured surface and knead it for approximately 5-7 minutes. The goal is a smooth, elastic dough that springs back when gently pressed.
Step 4: Lightly grease a clean bowl, then place the kneaded dough inside, turning it once to ensure it's coated. Cover the bowl with a clean kitchen towel or plastic wrap. Find a warm spot in your kitchen and let the dough rise for about 1 hour, or until it has visibly doubled in size.
Step 5: While your dough is on its first rise, prepare the star of the show
the raspberry filling! In a small saucepan over medium heat, combine the fresh or frozen raspberries, granulated sugar, cornstarch, and cinnamon. Cook the mixture, stirring frequently, for about 5 minutes. The raspberries will break down, and the mixture will thicken to a lovely jam-like consistency. Remove it from the heat and set it aside to cool completely before you use it.
Step 6: Once your dough has doubled in size, gently punch it down to release the accumulated air. Transfer the dough to a lightly floured surface and roll it out into a large rectangle, aiming for about 1/4 inch thick.
Step 7: Evenly spread the completely cooled raspberry filling over the entire surface of the dough, leaving a small, clean border along one of the long edges. This clean edge will help seal the roll.
Step 8: Starting from the opposite long edge (the one completely covered in filling), carefully and tightly roll the dough into a snug log. Pinch the seam firmly to seal it securely.
Step 9: Using a sharp, un-serrated knife or a piece of dental floss (for perfectly clean cuts!), slice the log into 12 equal pieces, each approximately 1 to 1.5 inches thick.
Step 10: Arrange the sliced rolls in a greased 9x13 inch baking dish. Cover the dish loosely with plastic wrap or a kitchen towel and let them rise again in a warm place for another 30 minutes, or until they look noticeably puffy.
Step 11: While your rolls are enjoying their second rise, preheat your oven to 350°F (175°C).
Step 12: Bake the rolls for 25-30 minutes, or until the tops are beautifully golden brown and the rolls are cooked through. Remove them from the oven and let them cool in the pan for about 10-15 minutes before adding the frosting.
Step 13: In a medium mixing bowl, combine the softened cream cheese, softened unsalted butter, powdered sugar, and vanilla extract. Beat these ingredients together using an electric mixer until the frosting is wonderfully smooth and creamy. If you find the frosting too thick for drizzling, add milk one tablespoon at a time until you achieve your desired consistency.
Step 14: Drizzle the prepared cream cheese frosting generously over the warm (but not scalding hot) Raspberry Cinnamon Rolls. Serve them immediately and prepare for pure joy with every sweet, tangy, and fluffy bite!