In a large mixing bowl of an electric mixer, combine yeast and warm water. Stir until the yeast has dissolved, then let rest for about 5 minutes until bubbly. This is crucial as it activates the yeast, ensuring a good rise!
While waiting, heat milk, cream, and butter in a large saucepan over medium heat. You want to scale the mixture and bring it nearly to a boil, stirring frequently. Remove from heat and stir in sour cream. Allow this mixture to cool to 110 to 115 degrees before adding it to the proofed yeast.
Once cooled, add the egg, vanilla, salt, and sugar to the yeast mixture. Stir well to combine all the ingredients evenly.
Gradually add flour, mixing until the dough starts to come together. Switch to a kneading attachment and knead for about 5 to 7 minutes until smooth and elastic. The mixture will seem runny, but resist the temptation to add more flour.
Cover the bowl with a clean kitchen towel and let the dough rise in a warm place until it has doubled in size, about 1 hour. This step is essential for achieving light and fluffy rolls.
After the dough has risen, sprinkle in baking powder and knead for another minute just to combine.
Divide the dough into two equal portions. On a generously floured surface, roll each portion into a 12-inch by 16-inch rectangle. This size will help create a nice swirl effect!
Brush each rectangle with about 1 tablespoon of melted butter. In a separate bowl, mix together 1/3 cup sugar and raspberry jam. Spread this mixture over the dough, leaving about 1 inch from the edges.
Carefully roll the dough tightly from the longer side, ensuring a nice tight swirl. Once rolled, cut each log into 12 slices, about 1 1/4 inches thick.
Place the slices onto two greased jelly roll pans, ensuring they are spaced out. Cover and let rise again until doubled, about 30 minutes.
Preheat your oven to 375 degrees. When ready, bake the rolls for 17 to 19 minutes until they are lightly golden on top.
While the rolls are baking, prepare the icing. In a large mixing bowl, whip together the softened butter and cream cheese until fluffy. Add in vanilla, powdered sugar, and milk, blending until smooth and well combined.
As soon as the rolls come out of the oven, frost them while they’re still warm. You want the icing to melt slightly into the warm rolls, creating a delicious layer of sweetness!