Add an egg, 2 yolks, lukewarm water, and 2 tbsp of vegetable oil to a stand mixer with the whisk attachment. Mix until combined.
Switch out whisk attachment with a dough hook. Add in flour and instant yeast. Run the mixer on low for 3-4 minutes. Then, rest the dough for 20 minutes while the flour hydrates.
In the meantime, soak raisins in hot water to plump them for 5 minutes. Then dry them on a towel until ready to use.
After dough rests, mix in sugar and salt, then run the mixer on medium for 9 mins. Transfer to a floured surface and hand-knead, adding flour if needed to prevent sticking. Lightly oil the dough and bowl, cover, and let rise for 1.5 hours until doubled in size.
Mix in your raisins. I like to roll out the dough, spread an even layer of the raisins, then roll it up like a cinnamon roll.
Divide dough into 4 pieces, then stretch them into 16-inch long ropes with the ends tapered.
Stack 2 baking sheets and top them with a layer of parchment/ baking mat. Place the challah on top. Cover with cling wrap and prove for another 3 hours.
Next, heat the oven to 350°F with the rack in the middle. Meanwhile, beat the remaining egg in a bowl. Brush over the challah, so you’ll get that gorgeous brown color.
Bake your challah bread for 35-40 minutes until the internal temperature reads 190F. It will turn a gorgeous golden brown.