In a dry skillet over medium to medium-high heat, brown the besan. Make sure to keep moving it around with a wooden spoon to prevent burning. This takes about 5-10 minutes to get medium brown and color and smell fragrant. Remove from pan into a bowl and set aside.
In the same skillet (no need to clean it out, add in the mustard seed and dry-fry about a minute.
Add the onion (if using) and peppers to the skillet with about 1/4 cup water. Add in the turmeric and chili powder and stir to combine. Cover and cook until tender (may take about 10-12 minutes). Add in the garlic (if using) and cook covered for an additional minute.
When the vegetable mixture is tender, add the browned besan over the top of it, the crushed peanuts, Garam Masala, some salt (start with 1/2 teaspoon and more if needed later), and the coconut sugar. Adding 1/4 cup of water at a time, stir the mixture together slowly. If needed add a tablespoon or 2 of water at a time to make sure the besan is moistened but not too sticky. You want it to surround the peppers but not become gluey in texture. So, add water a little at a time to get that consistency.
Serve with rice, chapatis, or roti for a full meal!