In a medium sauté pan, melt butter over medium heat. Add onion; cook, stirring occasionally, until tender and translucent, approximately 5 minutes. Add chutney, tomato purée, ¼ cup water, curry powder, vinegar, lemon juice, salt, pepper, and bay leaf, stirring to combine. Bring mixture to a simmer. Simmer, stirring occasionally, until sauce thickens, 8 to 10 minutes.
Transfer sauce to a heatproof bowl. Add cream, stirring to combine. Let cool completely. Discard bay leaf. Add chicken, walnuts, raisins, green onion, and parsley, stirring to combine.
Spread a thick, even layer of chicken salad onto 6 bread slices. Top each with another bread slice.
Using a long, serrated bread knife in a gentle sawing motion, trim and discard crusts from sandwiches. Cut each sandwich into 3 (approximately 3x11 ½-inch) rectangular sandwiches.
Serve immediately, or cover with damp paper towels, place in a covered container, and refrigerate until ready to serve.
Notes
*We used "Major Grey’s Chutney."
Recipe by TeaTime Magazine at https://teatimemagazine.com/curried-chicken-salad-tea-sandwiches/