Blanching means to remove their skins. Spread them on a baking sheet and bake the nuts in a 350-degree oven until toasted, 5 to 8 minutes. Remove them from the oven. Spread the nuts on a tea towel, then roll up the tea towel and roll the towel against a work surface -- this will rub off the skins. You'll need to shake out and wash the tea towel after but the filberts will lose their skins!