Heat the grill or tawa to high. To make the dressing, place all the ingredients in a food processor and blend until smooth, or use a hand-held mixer. Season to taste.
Place the garlic cloves on tawa or under the hot grill for 4-5 minutes until the skins are blackened, turning once. Let them cool enough to handle, then squeeze out the flesh and mash it.
Spread one side of the bread slices with the garlic paste, then cut the slices into bite sized portions. Arrange them in one layer on a baking sheet and toast on tawa or under the hot grill for 1-2 minutes, turning from time to time, until the croutons are golden brown.
Toss the spinach and apple together in a serving bowl, then scatter the garlic croutons on top. To serve, drizzle the dressing over and garnish with fresh chives.