Brioche Bagels

I recently saw brioche bagels at the grocery store and, quite frankly, they looked terrible. I was pretty sure I could make a vegan version that was so much better than whatever Loblaws was peddling. I was right! These are tender and absolutely delicious toasted with jam, or as a sandwich. They are the perfect addition to any brunch or lunch. The recipe is a Reinhart adaptation and mashup. You can also make two 1 lb sandwich loaves if that is more your thing. 
INGREDIENTS
Makes 8 large bagels
Sponge
– 2.25 oz bread flour
– 8 g instant yeast
– 4 fl oz lukewarm plain soy milk
Dough
– 2 oz cooked sweet potato
– 4.5 fl oz plain soy milk (cold), or aquafaba*
– 14.75 oz bread flour
– 1 oz sugar
– 1.25 tsp (10 g) salt (or generous .25 tsp (4 g) if using salted butter)
– 4 oz vegan butter, at room temperature**
Poaching Liquid
– enough water the fill your pot about 1.5″ high
– 1 tbsp baking soda
– 1 tbsp brown sugar
* I did not find any difference between soy milk or aquafaba in a blind taste test.
**You need a butter that will firm up when cold. I used home-made and Melt with great results.
METHOD
1. Whisk together the sponge ingredients in a stand mixer bowl until smooth. Cover and let rise for 45 mins.
2. Blend together sweet potato and milk (or aquafaba) with an immersion blender in a small container (I use a pyrex 1 cup liquid measuring cup) until very smooth. Whisk into the sponge.
3. Add the flour, sugar, and salt, Use the dough hook to bring the ingredients together into a rough dough. Make sure all the ingredients are incorporated. Let rest for 5 mins.
4. With the dough hook running on medium speed, add the vegan butter about 2 tbsp at a time, waiting for it to be incorporated into the dough before adding more. The dough will start out tough but will soften as it takes on more fat.
5. Once the butter is incorporated, knead the dough for 5-7 mins, or until smooth. 
6. Shape into a ball, place in a lightly oiled bowl, cover, and let rise for 60 mins. 
7. Divide the dough into 8 equal pieces. Shape each piece into a ball. 
8. Line a large baking sheet with lightly oiled parchment paper.
9. Pinch though the centre of the ball with your thumb and forefinger, then shape into a ring. (I find this method best because the final bagel is delicate and this allows it to withstand the poaching process without breaking apart). 
10. Place the shaped dough rings on the prepared sheet, mist with oil, cover with plastic wrap, and immediately refrigerate for 8 hours, or overnight. The bagels will have risen and firmed up in the cold.
11. When you are ready to bake, preheat the oven to 450 degrees. Get the poaching liquid simmering in a large pot. 
12. Add as many bagels as will comfortably fit in your pot (usually four), top side down (they should float). Poach for no more than 30 seconds, then flip over. Poach for no more than 30 seconds more, then transfer back to the prepared baking sheet. Repeat with remaining bagels.
13. Bake for 8 mins, then rotate the pan. If the bottoms of the bagels are browning too much, you can at this time place the baking sheet on top of an empty baking sheet to insulate the bottom. Bake for another 6-8 mins until golden. 
14. Let cool and serve!