Slice the onions, then season with salt and pepper. Microwave in a covered dish until tender.

Cook the bacon bits in a skillet until slightly crispy.

Layer the filo dough (or puff pastry) sheets, brushing a little butter between each one.

Mix the sour cream and mustard, then season lightly with salt and pepper. Spread the onions, bacon, and cream mixture over the dough sheets and bake in a convection oven at 400°F (200°C) for about 20 minutes.