Begin by heating the water for the 'cream' sauce in a 8-9 inch pan.
Add in the onion, garlic, thyme, pepper, and bay leaf.
Bring the mix to a simmer, then reduce the heat to medium low.
Cover the pan with a fitted lid, and let the onions cook for 20 minutes, stirring once or twice in the interim.
While the sauce is cooking, halve your Brussels sprouts and steam them in an appropriate pan for 10-11 minutes, until fork tender. Alternatively, you could boil them, but I feel they lose more nutrients that way.
Once the sprouts are steamed, deposit them onto a cutting board, and (when cool enough) chop them into bite-size pieces.
Oil or butter an 8 x 8 inch baking dish, and spread the sprouts across the bottom.
Preheat the oven to 400 degrees, at this time.
Once the onion mixture has cooked for 20 minutes, remove the bay leaf, and add it to a high speed blender along with the olive oil.
Blend until smooth, adding salt to taste. Add in a splash of water if needed for blending.
Pour the 'cream' sauce atop the Brussels sprouts, giving it a little mix with a spoon.
Top the mix with the cheese, mixing it in a bit as well, if you like.
Mix the breadcrumbs with the two tablespoons of olive oil and a dash of salt.
Spread the breadcrumbs atop the cheese.
Bake for 20 minutes until bubbly.