First chop the hard boiled eggs, add cheese, green chilies and coriander leaves... and keep it.
Then, in sauce pan, heat butter.
Add flour and cook for 2 -3 minutes, add salt, white pepper and mustard powder.. mix well.
Add milk, and stir continuously... make sure no lumps form... cook till thickens on low heat.
Add the egg mixture in it
Mix well... and transfer it in bowl an let it cool completely
Now, mix the bread crumbs and sesame seeds together
Start making the roll... add around 1 to 1 1/2 tbsp of mixture
Shape it like a spring roll.... make sure you cover the filling safely...
Now dip it in beaten egg ... cover all over
Then in bread crumb mixture
Repeat same process until your filling ends... you can freeze them at this stage
When, serving... deep fry them in hot oil.. give one side jut 15 - 20 seconds... or until get golden color on top
Serve warm and enjoy.