I finally found plain brioche in Salt Lake thanks to Tamara's recommendation (Gourmandies/The Bakery). Since I knew the brioche was going to be used for French Toast (best with slightly stale bread), I bought the day-old version at half the price. It was a hit at breakfast! If you live in an area where plain brioche is unavailable, you can substitute challah for a similar flavor and texture.
Brioche French Toast
3 large eggs
1 cup milk
3/4 tsp kosher salt
1 tablespoon sugar
1/4 tsp ground cinnamon
1 tsp pure vanilla extract
7-8 slices brioche, cut into 3/4 inch pieces
butter for griddle
1. In a large baking dish, combine the eggs, milk, 1/4 tsp salt, sugar, ground cinnamon, and vanilla extract. Beat thoroughly with a wire whisk until well incorporated.
2. Soak four 3/4 inch slices of brioche in the egg mixture about 3 minutes, turning once to soak other side.
3. Meanwhile, in a large skillet set over medium heat, melt 1 tablespoon butter. Add the soaked bread and cook until golden brown on both sides--about 2 to 3 minutes per side. French toast can be kept warm in a 275 degree oven for up to 15 minutes. Make sure you use an ovenproof platter :)
-from the Martha Stewart Living Cookbook, 2000 version