Peel and core apples. Finely chop and slice 2 qts. Place in separate containers and sprinkle with lemon juice. 

 

Place muffin mix in mixer. Combine eggs and water. Gradually add to dry ingredients while mixing on low. Mix until dry ingredients are moistened. Add chopped apples.

 

For topping, combine and mix together brown sugar, flour, cinnamon, vanilla, salt, 2-1/4 cup butter and walnuts until crumbly. Portion one half of batter (3 qts) into each of two 18 x 26 x 1 inch sheet pans. Evenly sprinkle batter with 2-1/2 cups topping, top with 1 qt sliced apples, 1/2 cup melted butter, and 1-1/2 cup topping. Bake at 375 degrees F for 30 minutes or until lightly browned. Cut each pan into 50 portions.