How to Make It
In a bowl, combine the sardines, onion, chiles, radish, lemon juice and parsley.
In a small bowl, using the back of a spoon, mash the garlic to a paste with a pinch of salt. Whisk in the mayonnaise, mustard and the 1 tablespoon of olive oil and season the aioli with salt.
Preheat the broiler. Brush the bread on both sides with olive oil and broil, turning once, until lightly toasted. Transfer the toasts to a work surface and spread with the aioli. Mound the sardine mixture on top, cut each toast in half and serve right away.