Preheat oven to 425 degrees F.

Combine heavy cream, milk, and jasmine tea in a heavy bottomed pot. Bring to a simmer over low heat and heat for 5 minutes. Turn off the heat and let sit for 1 hour. Strain tea leaves and discard, reserving infused cream.

Place grapes in cast iron pan. Cut 2 tablespoons butter into small chunks and place on top. Sprinkle brown sugar on top of grapes and roast for 25 minutes, flipping grapes over halfway through. Remove grapes from pan and add 1 tablespoon honey to remaining juices. Bring to a simmer over low heat for 1 minute or until juices become syrupy. Remove from heat and keep warm.

Whisk together tea infused cream with vanilla, eggs, and 1 tablespoon sugar. Dip bread slices in batter, making sure to coat both sides.

Heat griddle over medium heat and melt about 1 tablespoon butter. Cook french toast until golden brown on both sides, about 4-5 minutes. Remove from heat and place on serving platter. Top french toast with roasted grapes, a dollop of mascarpone, and syrup. Serve immediately.