When I make corned beef I cook it in Guinness and water. Makes a lovely brown liquor.But as a side you don't need. You've got the potatoes and carrots and the cabbage of course. But try this. Put the potatoes and carrots only during the last hour, that eay they won't be mushy.And then take a bowl and rub it with fresh garlic. Toss in the hot potatoes with a pat of compound butter (parsley/butter/salt/pepper). This brings a special freshness to a dish that is rather homely.