Pre-heat oven to 375ºF.
Mix brussel sprouts, butternut squash, shallots, garlic cloves, salt, olive oil in a bowl. Transfer to a baking sheet and roast for about 20 minutes until vegetables are softened.
Heat a nonstick medium skillet over medium heat. Add walnuts to skillet and toast them shaking the pan around every so often for about 8 minutes until nuts are fragrant and slightly browned.
In a small pan, add butter and whisk continuously over medium high heat until it begins to get golden. When you start noticing brown bit at the bottom of the pan, take it off the heat. Toss walnuts with vegetables and brown butter. Serve