Select “Steam” function on the Instant Pot pressure cooker.
Set the timer to 5 minutes with high-pressure settings.
Add 1 cup water to the cooking pot and place the steamer basket above it.
Place diced and peeled vegetables in the steamer.
Seal the lid and cook for 5 minutes.
Release the steam through natural pressure release.
Drain the vegetables and transfer them to a bowl.
Heat butter in a saucepan over medium heat.
Add garlic, Béchamel sauce, combined cheese and nutmeg powder.
Mix well until smooth.
Stir in salt, pepper and potatoes.
Pour this mixture into a shallow casserole dish.
Top it with an even layer of breadcrumbs.
Bake for about 4 to 5 minutes at 350 degrees F in a preheated oven.