RHUBARB QUICK JAM

1. Combine the rhubarb, sugar, and salt in a medium saucepan. Heat over medium heat, stirring frequently, until the mixture comes to the boil. Reduce the heat slightly, and cook for a further 10-15 minutes, stirring often, until very thick and jammy. Remove from the heat and allow to cool before stirring in the vanilla bean paste. Set aside to cool completely. Store in a jar in the fridge until ready to use.

BRIOCHE DOUGH

1. In a small bowl, combine the yeast, milk and 2 Tbsp of the sugar. Mix well, and leave to sit for 10-15 minutes, or until foamy.
2. In the bowl of a stand mixer fitted with the dough hook, combine the flour, salt, and remaining 2 Tbsp sugar. Mix briefly to combine. Add the eggs, vanilla, and foamy yeast mixture to the bowl. Mix on low for 2-3 minutes, until the dough is starting to come together. It may look slightly dry but do not worry - it will mix together nicely in the next steps. Increase the mixer speed to medium, and mix for another 10 minutes, until the dough is soft and smooth. 
3. Reduce the mixer speed to low, and add the butter a little at a time, waiting until it is fully incorporated into the dough before adding the next piece. This process should take 3-4 minutes. Once the butter is fully incorporated, increase the mixer speed to medium, and mix for a further 5 minutes, until the dough is very soft and smooth. 
4. Transfer to an oiled bowl, and cover tightly with plastic wrap. Place in a warm spot until doubled in size, approximately 1 - 1 ½ hours. 

ASSEMBLY AND BAKING

1. Lightly grease a 9" x 13" baking dish or pan. Turn the brioche dough out onto a lightly floured surface, and pat into a rectangle. Roll out to a 24" x 18" rectangle, using a bench scraper to help keep the edges square. 
2. Spread the rhubarb quick jam evenly over the surface of the dough, and, starting with a long end, roll the dough up into a tight sausage. Cut the sausage into 2" lengths (I find cutting the whole thing in half, then each half into two, and then each quarter section into 3 works best). If your sausage is not 24" long (lol), measure the length first before you cut, and divide the length by 12 so your pieces are even. 
3. Arrange each bun in your prepared baking dish. Cover with plastic wrap and leave to rise in a warm spot for 45 min to an hour, or  until they have gone puffy, and when lightly poked, your finger leaves a slight indentation that bounces back. This second proving time will depend on the weather - it will go much quicker in warmer climates.
4. Toward the end of the second proof, preheat the oven to 350˚f / 180˚c. 
5. Remove the plastic wrap, and bake the buns for 35-45 minutes, or until golden brown (finished internal temp of 200˚f). If you think they are browning too quickly, tent with foil after 20 minutes. While the buns are baking, make the vanilla bean mascarpone frosting. 
6. Remove the buns from the oven, and allow to cool for 15 min before frosting generously with the frosting.

VANILLA BEAN MASCARPONE FROSTING

1. Place all ingredients in the bowl of a stand mixer fitted with the whisk attachment. Whip until smooth and fluffy. Taste and adjust sugar content if necessary.
2. Spread generously over the buns. Serve immediately.
3. Store leftovers in an airtight container. Briefly rewarm before eating.