1Toast the walnuts by spreading them on a parchment-lined rimmed baking sheet and toasting in a 350F oven for 6-7 minutes, or until golden and fragrant. If you have a toaster oven, that works too.
2Melt the butter in a small saucepan over medium-high heat and after it melts, continue cooking it, swirling the pan often, until it foams and turns a nutty brown. Whisk in the syrup, icing sugar and vanilla. Bring to a boil and simmer for 30 seconds.
3Spread the toasted walnuts out on the lined baking sheet and pour the butter mixture overtop, trying to cover as much of the nuts as possible. Stir a bit on the sheet with a spoon so that it clumps up and coats (or at least touches) as many of the walnuts as possible. Let cool, then break into chunks. Try to share.