Bring pot of water to a boil over high heat. Blanch broccoli for 2 minutes and immediately drain and plunge in ice water. Broccoli should be bright green and tender-crisp. When broccoli has cooled, drain well. Season with salt and pepper and set aside.
Make onion topping. Heat 1 tablespoon oil in a large saute pan over medium heat. Saute sliced shallots until partially cooked, about 2-3 minutes. Remove from heat and transfer to a bowl.
In the same pan, heat another tablespoon oil over medium heat. Add panko and toast until golden brown, stirring frequently. Remove from heat and transfer to same bowl with shallots. Add almonds, grated parmesan, Italian seasoning, salt, and pepper, tossing to combine. Set aside.
Melt butter in a large sauce pot over medium heat. Add garlic and saute until aromatic, about 30 seconds. Add flour, whisking until well combined with butter. Slowly add vegetable broth, whisking constantly to dissolve flour butter mixture. Add milk and bring to a simmer. Add parmesan and pinch of nutmeg and continue to simmer until thickened, about 4-5 minutes. Season with salt and pepper and remove from heat.
Pour parmesan sauce over broccoli, tossing to coat. Transfer to a 9x13 baking dish and spread broccoli in an even layer. Top with shallot breadcrumb topping and bake for 20-25 minutes or until golden brown and crispy on top. Serve.
Notes
To make this dish ahead of time, you can prepare the parmesan cream sauce and cook the broccoli the day before. Toss the broccoli with the cream sauce and transfer to a baking dish. Cover and let sit in the refrigerator until ready to bake. Right before baking, sprinkle the shallot breadcrumb on top and bake.