Preheat the oven to 300 F. Grease a loaf pan with butter and set aside. Line a large rimmed baking sheet with parchment paper.

Use a large chef's knife to cut the babka into slices 1-inch thick. Lay out the slices on the prepared baking sheet and set aside.

In a large bowl, whisk together the eggs, cream, vanilla and cinnamon. Dip the babka slices, 1 slice at a time, in the egg mixture. Coat both sides for about 30 seconds or so, allowing the babka slice to absorb some of the egg mixture without getting too soggy or falling apart. Repeat with all of the slices, placing them back on the parchment-lined baking sheet while you finish.

In a large saute pan, heat 1 tablespoon of butter over medium-high heat. Once the butter is melted, add 2 slices of babka and fry, turning once, 1 to 2 minutes per side. Be careful that the heat isn’t too high to avoid burning the babka slices. Transfer the browned slices to your prepared loaf pan, lining up the slices to re-create the original loaf shape. Continue heating 1 tablespoon of butter at a time in a pan and browning the babka slices in batches, 2 slices at a time, and transferring them to the loaf pan. Use all of the French toast slices to fill the loaf pan.

If serving right away, place the loaf pan in the oven, uncovered, for 5-7 minutes longer. This will heat up all the slices to the same temperature and make them nice and toasty.