To toast on the stove:

1. Heat oil in a large heavy skillet over medium heat, 2-3 minutes.
2. Add numbing peppers and chili flakes in the skillet. Stir until fragrant, about 1-2 minutes.
3. Add walnuts, sprinkle with salt and sugar. Stir frequently to prevent walnuts from burning. Toast for 1-2 minutes or until the walnuts are golden brown. Transfer to a plate to let cool. Taste and add more salt if desired.

To toast in the oven:

1. Heat oven to 350°F.
2. Toss walnuts with oil and all spices together in a mixing bowl.
3. Spread nuts in a single layer on a cookie sheet lined with parchment paper (for easy clean-up).
4. Place in the oven and roast for 5-10 minutes until the nuts are golden brown. Stir or shake the pan during toasting in order to make them brown evenly.
5. Remove from oven and let cool before enjoying.