Grease heavily the back of a big heavy bottomed pizza pan or thali and rolling pin, with two tbs spoon oil. (See notes)
Dry roast sesame seed in a heavy-bottomed pan on medium-low flame for 3-4 minutes with constant stirring until light toasted. Remove toasted seeds to o a plate and set aside.
Keep a bowl with water ready for testing jaggery caremelization.
Put grated jaggery in a heavy-bottomed wok. Melt jaggery on medium flame, while stirring constantly. When jaggery is melted, drizzle oil along the side of the wok. Keep stirring.
Now increase the heat to medium-high so jaggery starts bubbling and caramelizing, stir well so jaggery is uniformly caramelized.
Test jaggery in water by dropping a small drop and then press it. If the drop form a soft lump, cook more. If it turns hard immediately then your jaggery is ready.
Mix in roasted sesame seeds and quickly pour all mixture on greased thali. With greased rolling pin make ⅛ inch flat sheet.
Apply a thin layer of oil on top of the brittle for the glazed look.
Make cutting marks while the brittle is still hot. Let the brittle cool completing before removing from thali.
Store in airtight container at room temperature.