Using a separate bowl whisk together flour and salt.
Using dough hook attachment on medium speed add eggs into yeast mixture one at a time. (option to beat your eggs with a fork first)
Then slowly spoon flour into stand mixer, continuing on medium speed.
Once all butter is incorporated, dough should be sticky, but pulling away from the edges of the bowl.
If its too wet, add a Tbsp of flour at a time while mixing. DO NOT make dough dry. It should be tacky and stick to your hands but easily pull off.
Prepare two 9 inch loaf pans with baking spray and strips of parchment paper. Set aside.
Bake Babka loaves on middle rack for 30-40 minutes. Check loaves at 20 minutes and if they are browning too quickly cover with aluminum foil. Use a thermometer to check the temp of your loaves at the 30 minute mark. Bread is baked at 190 F (87 C).