1. Preheat the oven to 395 degrees F (200 degrees C).
Prepare your veggies as follows:
Peel and finely dice the onion.
Peel and mince the garlic.
Cut the Brussels sprouts into quarters.
Roughly chop the bacon to preferred size and separate any strips that are stuck together.
Heat the olive oil in a medium-size pan over medium-low heat. Add onion and garlic, and cook until the onion is translucent and fragrant.
Add the bacon to your pan and fry until golden and crispy.
Add Brussels sprouts, salt, black better, and half of the thyme. Cook for 10 minutes, stirring occasionally, until the Brussels sprouts have softened. The Brussels sprouts’ green color will intensify as they cook, and this is a good indicator that they’re done. Once the Brussels sprouts are tender, scoop out and set aside in the mixing bowl.
Reduce heat to low. Make a bechamel sauce by adding the butter to the pan and, after the butter has melted, add the flour. Stir well and gently fry, whisking constantly, until the bechamel sauce is golden.
While whisking, pour in the evaporated milk. Season with a dash of freshly-ground salt and pepper.
Pour the bechamel sauce into the mixing bowl with the Brussels sprouts and bacon. Stir until well-mixed.
Pour the Brussels sprouts mixture into the 9x13 pan and top with the grated parmesan. Sprinkle the rest of the thyme over top.
Bake for 15 minutes or until the cheese is golden and bubbling.