In large bowl, whisk together 3 cups of flour, baking powder, 1/2 cup ofthe sugar and yeast until fully combined. In a small pot over medium-low heat, heat the buttermilk, sea salt and1/2 cup of butter until the butter has just melted and the salt is dissolved,and it reaches a temperature of approximately 115°F to 118°F. While the milk is warming, preheat the oven to 250°F.In a 9- by 13- pan or divided between two 9-inch round cake pans, addthe remaining sugar, 1/4 cup of butter and corn syrup. Bake to melt the butter,about 10 minutes. Remove from the oven and turn the oven off. Stir the sugarmixture to combine and allow the sugar to continue to melt.
Make a well in the centre of the flour mixture and pour in the warmedmilk and add the eggs. Starting in the centre, whisk the dry ingredients withthe wet ingredients, working your way outwards to incorporate all of the dryingredients. The dough will be very sticky. Sift in 1 cup of flour and stirwell with a wooden spoon. Place half of the remaining flour on the counter andturn the dough onto it, then sprinkle the remaining on top. Knead the dough for10 minutes, until smooth and elastic. Oil a large mixing bowl and place thedough in the bowl turning to coat. Cover with plastic wrap and set on top ofthe stove, or close to the oven vent to rise for 15 minutes, you can also setthe bowl in the warm oven if it’s cool and drafty in your kitchen.
In a small pot, combine the partridgeberries, orange juice and the zest.Simmer over medium heat until the berries just start to pop. Gently mash theberries and increase the heat to medium-high and bring the mixture to a boil.Boil until it has the consistency of thick jam, and almost all of the liquidhas boiled off. Remove from the heat and set aside.
Remove the dough from the bowl and lay on a lightly floured surface.Using a rolling pin, roll the dough into a 12- by 18-inch rectangle shape,spread evenly with the remaining butter and then the partridgeberry sauce. Rollup the dough starting from the long edge creating a long log, turn the log ifneeded so it is seam side down. Slice the log into 1 inch wide slices, thenplace the slices cut side up in the baking pan, nestling them together on topof the caramel. If there is a bit of space between them that is ok, they willrise together.
Cover with a tea towel and let rise in a warm place for 25 minutes, oruntil the rolls are starting to puff up beyond the edge of the pan. We like toplace them on the oven or in the oven to rise. If they are in the oven, removebefore preheating.
Preheat the oven to 350°F.
When the rolls have risen, bake until golden brown on top and the doughhas set, 25 to 30 minutes. The cooking time can sometimes be faster for a glassPyrex pan, so bake until the sides and top are lightly golden, closer to 20 to 25 minutes.
As soon as they are removed from the oven, run a butter knife or spatulaaround the outside. Place a serving platter or cutting board over top of thepan and using oven mitts flip the platter over allowing the rolls to turn ontothe platter, carefully remove the baking pan and scrape any remaining caramelfrom the pan over top of the rolls. Let sit 5 minutes to cool slightly andserve.
Rolls will keep covered at room temperature for up to 3 days althoughthey are best enjoyed the day they are made.