Heat a pan (non stick preferably), add 1 tsp oil/butter, add garlic, saute for a few seconds and add spinach leaves.
Cook the leaves on high flame till they turn soft and the water evaporates (reduce in quantity).
Add sweet corn, mix well and remove it from the flame. Keep the sauteed spinach-corn in another bowl and in the same pan add butter.
When the butter melts, add maida/all purpose flour and mix well. Make sure the heat is low while making the sauce.
Slowly start adding milk to the butter and maida, making sure no lumps are formed. When the sauce turns very thick, add spinach-corn along with salt and pepper. Mix it well and switch off the flame.
Now, toast the bread slices on a tawa or toaster. Remove the slices from the tawa/toaster and apply butter.
Take a spoon and apply the prepared creamy spinach and sweet corn mixture to the toasted bread. Put another slice of bread above the spread and press lightly. Cut it diagonally and serve.
If you want tp pack this in lunch box then don't use toasted bead. Just make sandwiches using plain bread and its good to go.