Start with the broccoli. I like to sauté in a skillet with a drizzle of olive oil for about 10 minutes. Alternatively, you can steam the broccoli. With either method, the goal is broccoli that is crisp-tender.
Add the prepared broccoli to a 9 inch pie plate. Add butter to a shallow pan and sauté onion in butter until tender. Stir in garlic and cook for one minute until fragrant. Sprinkle onions and garlic over broccoli.
Whisk together remaining ingredients and pour evenly over the broccoli mixture.
Bake at 350 ℉or 30-35 minutes until it is lightly browned and a knife inserted into the center comes out clean.