In a small bowl mix the mascarpone and lemon curd together, making sure it is well combined and set aside
Heat ½c of the raspberry rhubarb jam with 1 tablespoon water either in a small saucepan or microwave safe bowl, stirring until slightly thinned. Keep warm
In a larger , flat bottomed bowl or dish scrape the seeds of the vanilla beans into it and add the 1 tablespoon of sugar. Rub the vanilla beans and sugar together until its well dispersed and fragrant. Add in 2 whole eggs and whisk and then ½ cup milk the pinch of sea salt and whisk until combined. If using a larger loaf, more than 4 pieces, use the larger amounts listed.
Take each large slice of bread and cut a slit on one side about 3” wide and about more than halfway inside the bread creating a “pocket” being careful not to slice all the way through the bread. Spoon in 2-3 tablespoon of the curd mascarpone mixture.
Heat a cast iron pan over medium heat and melt 1 tablespoon butter.
While the pan is heating, carefully dip the stuffed slice of bread in the egg mixture coating each side well, making sure you don’t over saturate the bread.
Place in the pan and repeat with 1-2 more slices of the bread. You don’t want to overcrowd. Cook for a few min and carefully flip and cook on the other side a few more minutes until golden brown.
Top each slice with some of the raspberry rhubarb sauce and powdered sugar. Serve hot!