Transfer ice cream to mixing bowl and add jelly. Using a rubber spatula, fold in the jelly so it is streaky and not uniformly mixed. Return to the pint container and freeze until set, about 2 hours.
Melt butter in a small skillet over medium-high heat. Add bread cubes and stir to coat bread on all sides. Continue stirring, until bread is golden brown on all sides. Remove from heat. Sprinkle with 3 tablespoons sugar and set aside.
Combine heavy cream and brown sugar in a saucepan and bring to a boil. Reduce heat to simmer, add peanut butter, and stir until combined and melted. To serve, scoop ice cream into serving bowls, drizzle with peanut butter sauce and top with croutons.