Chicken tikka and mango chutney is the tikka sandwich whose defining move is sweetness set against spice rather than coolness against it. The chutney is not a condiment added at the end for interest. It is the structural counter the whole sandwich is built around: a thick, sugary, slightly acidic mango preserve that meets the charred, dry, savoury spice of the tikka head-on and turns a one-note filling into a sweet-and-hot one. Take the chutney away and you are left with dry spiced meat and bread; the chutney is the part that makes the rest cohere into a sandwich worth naming.
The craft is using the sweetness as both flavour and glue without letting it swamp the build. Mango chutney is dense and clinging, which is an advantage here: spread in a measured layer it coats the dry tikka pieces and bridges them to the crumb the way a thin sauce never could, adding back the moisture the meat lacks while carrying the sweet counter into every bite. It has to be measured, though, because chutney laid on too thick reads as jam and slides, and its sugar and acid will soak soft bread if there is nothing between them. The bread is plain and soft so it yields to the firm meat, buttered to the edges first as a barrier against the chutney's moisture and its acidity. The tikka is diced small so no bite is all char, and a dry salad leaf or a little cucumber is often run alongside for a crisp, neutral break between the sweet and the spice. Pressed and cut, the sandwich should read sweet first, then hot, then savoury, in that order.
The variations are the rest of the tikka family, each defined by what it sets against the spice. Chicken tikka and raita answers with cooling yoghurt rather than sweetness; the plain chicken tikka sandwich fights the dryness with a bound dressing alone; the chicken tikka wrap rolls the same pairing into a flexible bread. Each deserves its own article rather than being crowded in here.