For the biscuits: Preheat the oven to 400 degrees F.
Whisk together the flour, baking powder, 1 tablespoon of the sugar, and the salt in a medium bowl. Using a bowl scraper or your fingers, mix in the butter until the mixture resembles a coarse meal (using your fingers will yield a more cake-like texture). Make a well in the center, pour in the milk and stir until just combined.
Turn the dough out onto a floured work surface and knead 5 or 6 times. Roll into a 10-by-14-by-1/4-inch rectangle.
Mix together the mascarpone, cinnamon and the remaining 3 tablespoons sugar in a small bowl until well combined. Gently spread the mixture onto the rolled-out biscuit dough, leaving a 1/2-inch border. Sprinkle with the raisins and then roll the dough into a long cylinder. Transfer to a baking sheet and freeze for 20 minutes.
Set the dough cylinder on a floured work surface and slice into 8 equal pieces. Place cut-side down on a parchment-lined baking sheet, spaced 1 1/2-inches apart. Use the palm of your hand to gently press the biscuits into 1-inch-thick disks.
Bake until the tops start to brown, 20 to 25 minutes.
For the caramel: Whisk the cream and the instant tea together in a small bowl until the tea has dissolved (or add to a Mason jar and shake).
Without stirring, heat the sugar in a dry pan over medium heat until liquefied and starting to brown, 6 to 10 minutes. (When the edges begin to brown and the sugar is liquid, go ahead and stir to ensure even browning.) Continue cooking until copper colored, 1 to 4 minutes. Immediately turn off the heat and VERY CAREFULLY stir the cream-tea mixture into the hot sugar. Add the vanilla and stir until smooth. (If lumps form, turn the heat back on to low and stir until dissolved.) Set aside to cool a bit.
Drizzle the biscuits with the caramel and eat as soon as cool enough not to burn the roof of your mouth.