Brussels Sprouts & Brie Gratin

Does anyone know what a "firm" Brie round is? I just bought a round. And it was not what I'd call firm because it was difficult to slice (because of it's not firmness). It still worked ok, but the one I bought was definitely more for dips and spreading on a cracker. Maybe it was just my limited options at WinCo? 

• 2 Tbsp extra-virgin olive oil
• 3 Tbsp unsalted butter, plus more for greasing baking dish
• 3 cups thinly sliced yellow onions (from 2 medium onions)
• 2 1/2 kosher salt, divided
• 3 Tbsp water
• 2 lb brussels sprouts, ends trimmed
• 1 cup heavy cream
• 1 tsp freshly ground black pepper
• 1 Tbsp lemon zest plus 3 Tbsp fresh juice from 1 lemon
• 6 oz Parmesan cheese, freshly grated, divided
• 1 (8-oz) firm Brie cheese round, sliced into 1/4 inch strips
• 1 cup fresh bread crumbs 

Heat oil and butter in a large skillet over medium high, stirring occasionally, until butter is melted. Reduce heat to medium low and add onions and 1 1/2 tsp salt. Cook, stirring occasionally, until onions are caramelized, about 45 minutes, adding 1 Tbsp of water every 15 minutes. Remove from skillet from heat, and set aside to cool. 

While cooking onions, bring a stockpot of salted water to a boil. Prepare an ice water bath. Cook brussels sprouts in boiling water for 5 minutes. Using a slotted spoon, transfer sprouts immediately to ice water bath until cool to touch, 3-5 minutes. Transfer sprouts to a large kitchen towel, patting well to dry. Slice sprouts in half lengthwise. 

Preheat oven to 400 degrees. Grease a 13x9 inch baking dish with butter. Stir together sprout halves, cream, black pepper, lemon zest, and lemon juice, 2 1/2 cups of Parmesan, and remaining 1 tsp of salt in a large bowl to combine. Fold in caramelized onions. Transfer to prepared baking dish. Top evenly with slices of Brie, bread crumbs, and remaining 1/2 cup Parmesan. 

Bake until liquid is bubbling and surface is a deep golden brown, 20-25 minutes. Let cool 10 minutes. Serve warm. 

NOTES: This was very lemony. I like lemon, but even I could have used less. I didn't adjust the recipe above, but if you are not a fan of lemon, I'd definitely lesson the amount. 

Serves 8

Prep Time: 45 minutes

Total Time: 1 hour, 10 minutes

Recipe from People Magazine, Gaby Dalkin