Preheat oven to 300 degrees F.
Spread cut challah on a baking sheet and toast for 25-30 minutes or until lightly toasted and dry. Let cool completely.
Increase oven temperature to 350 degrees F. Grease a 9x13 baking dish with butter or cooking spray.
Heat milk in a medium saucepan over medium heat until it comes to a bare simmer. Remove from heat and whisk in sugar, salt, and vanilla, whisking until sugar is dissolved. Add loose tea leaves and let sit for 25 minutes.
Strain infused milk, discarding tea leaves. Whisk eggs and egg yolks into tea mixture until well combined.
Lay toasted challah in prepared baking dish in an even layer. Pour tea egg mixture on top, tossing the bread to coat. Add blueberries, gently tossing all together. Let sit for 20 minutes.
Bake bread pudding for 35-40 minutes or until golden brown and set. Remove from oven and let cool for 20 minutes.
Meanwhile, make rhubarb creme anglaise. Heat rhubarb with sugar and water in a medium saucepan over medium heat. Simmer until rhubarb is softened, about 5 minutes. Remove from heat and puree rhubarb until smooth.
Heat heavy cream in a medium saucepan over medium heat until it comes to a bare simmer. Whisk egg yolks and sugar in a medium bowl until well combined. Slowly add warm heavy cream to yolks, whisking constantly. Add a pinch of nutmeg and pureed rhubarb and return to the stove. Continue to simmer for 3-5 minutes, whisking constantly, until thickened. Remove from heat and stir in honey. Serve bread pudding with creme anglaise on the side.