Cooke Brussels sprouts in a large pan of boiling, salted water for 2 minutes. Drain well.
Heat oil in a large frying pan over medium heat. Add sage leaves and hazelnuts. Stir for 1-2 minutes or until hazelnuts are golden and sage is crisp. Remove from heat and transfer nuts and sage to a paper towel-lined plate.
Return pan to cooktop over high heat. Add Brussels sprouts and cook for 4 minutes, tossing regularly, or until golden and slightly charred. Transfer to a serving platter and top with sage, hazelnuts and crumbled cheese.
If you are not a fan of blue cheese, you can swap it for a creamy brie or camembert, or even a low-fat feta.