Preheat oven to 180 degrees and grease 12 hole large muffin tin.
First make topping: Place brown sugar, flour, butter and walnuts into TM bowl. Set lid to closed lid position and turbo 3-5 seconds or until ingredients combine and resemble coarse breadcrumbs. Set aside.
Chop white chocolate in TM bowl on closed lid position, turbo 3-5 seconds. Place remaining ingredients into TM Bowl. Combine ingredients on Reverse/Speed 6/10-20 seconds until combined but still lumpy. Pour mixture into greased muffin tins. Top with combined topping ingredients. Bake 20 minutesor until muffins are brown and firm. Allow to stand in tins for 2 minutes, then turn out onto a wire rack and leave to cool.