Combine chantarelle and porcini mushrooms, stock and the water in medium saucepan; bring to the boil. Reduce heat; simmer, covered.
Meanwhile, melt 30g of the butter in large saucepan; add remaining mushrooms to pan. Cook, stirring, until mushrooms are tender and liquid evaporates; remove from pan.
Melt remaining butter in same pan; cook shallots and garlic, stirring, until shallots soften. Add rice; stir to coat rice in butter mixture. Return mushrooms cooked in butter to pan with wine; bring to the boil. Reduce heat; simmer, uncovered, until liquid has almost evaporated. Add 1 cup simmering stock mixture; cook, stirring, over low heat, until stock is absorbed. Continue adding stock mixture, in 1-cup batches, stirring, until absorbed between additions. Total cooking time should be about 25 minutes or until rice is tender. Stir in cheese and the chives.