Step 1

In a small dry saucepan, toast hazelnuts over medium-high heat, until they just start to brown and become fragrant, about 1 1/2 to 2 minutes. Remove from heat and immediately transfer to mortar and crush with pestle to form coarse powder. (Alternatively, use a spice grinder.)

Step 2

Trim and discard ends of cucumbers. Cut each cucumber in half lengthwise and then into thin slices. Place sliced cucumbers in a medium mixing bowl.

Step 3

Using a whisk or fork, thoroughly mix mustard oil and lime juice in small bowl and pour over cucumbers. Add toasted hazelnuts and pepper flakes. Stir to combine. Season to taste with salt. Serve immediately.