Preheat the oven to 350°F (175°C).
Spread the almonds on a rimmed baking sheet and toast for about 8 minutes, until fragrant and golden. Transfer the almonds to a plate to cool. Shred the chicken meat using 2 forks or, if you prefer, cut it into pretty little cubes. Snack on or discard the skin and discard the bones. Place the chicken in a large bowl.
To make the curry dressing, pulse the mayonnaise, yogurt, chutney, lemon juice, curry paste, and almonds to a chunky texture in a food processor fitted with a metal blade. (Alternatively, you can mix this by hand, cutting up any large pieces of chutney, if needed.) Stir in the cranberries, if using.
Mix the curry dressing with the chicken, adding mayonnaise or yogurt, if needed, to generously coat the chicken. Season to taste with salt and pepper and additional chutney or lemon juice, if desired. (You can cover the chicken salad with plastic wrap and refrigerate for up to 3 hours.)
Cut the core from the radicchio and carefully pull apart the leaves. (For the first few leaves, you will need to roll back the edges to peel them off the head without tearing them. If you are using Treviso, cut off the bottom inch of the head, and the leaves should easily fall apart.) The larger leaves are best for plated presentations, while the smaller ones work well as finger food for hors d'oeuvres. Trim the largest leaves, if needed, to make them more manageable. (You can place the radicchio leaves in a resealable container, cover with a damp paper towel, cover tightly, and refrigerate for up to 3 hours.)
To serve, spoon the curried chicken mixture into the radicchio cups and garnish each with a sprig of cilantro. After you have filled the radicchio leaves, stack any remaining ones, roll them up into a tight cigar shape, and cut crosswise into thin ribbons to use as a bed for your platter or entrée-size salad. Arrange the cups on the platter and garnish with additional ribbons of radicchio, cilantro sprigs, and small bunches of grapes, if using