Dry roast the sesame seeds: Take seeds in a pan and dry roast on medium-low heat for about 3-4 minutes with stirring constantly. We are not looking for color change. Just warming up slightly.
Cool & Grind: Remove it to a plate and let it cool down. Then grind it coarsely.
Melt Jaggery: Now take ghee and jaggery in a pan on medium heat. Let the jaggery melt.
Add ground sesame seeds: Immediately add coarsely ground til. Mix it quickly and turn off the stove.
Cool to warm: Remove it to a plate and let it cool to touch (warm).
Mix in milk: Now as soon as you can handle the mixture, try pinching a small portion, if it comes together like a ball then you are good. If it looks dry like mine then start adding a teaspoon of milk at a time and keep mixing. The mixture may get sticky, but now you can shape.
Shape: Grease the modak mould using ghee and start shaping. Keep the mould close, start stuffing and pressing tightly from the bottom hole. Smooth out the bottom surface, open and unmould carefully. Repeat the same and keep arranging on the plate. As it cools down completely, it will firm up more.
Notes
On regular days, you can shape into the ladoo and serve to your kids as after school snack.
Do not let the melted jaggery boil otherwise, the modak will become hard like a rock.
I like some texture in my til modak so I ground the seeds coarsely. If you want you can make a fine powder.