For the sauce: Heat (about one tbsp) unsalted butter. Add in one tbsp all purpose flour. Mix it until it becomes like crumbling mini doughs. Add in about 150-200 ml (amount depends on how thick you want the sauce to be) vegetables stock (or any soup stock, I used apple chicken soup). Stir until smooth (as in minimal lumps). Add in few dash of liquid aminos (for adults, you can add in oyster sauce). Done.
Video of the 16m11d tasting it <here>
And my portion of dinner: