Here is the recipe from the Jiffy Blueberry Muffin Mix box. I hope it's the right one.
1 7 ounce package Jiffy Blueberry Muffin Mix
1/4 cup milk
1 egg
2 tablespoons melted shortening
Preheat oven to 350 degrees. Grease an 8" square pan. Stir ingredients until well mixed and spread in pan. Sprinkle with the topping and bake 20-22 minutes until lightly browned. Serve warm.
Topping:
1/4 cup brown sugar
1/4 cup chopped nuts (I use pecans)
1 teaspoon cinnamon
1 tablespon Jiffy baking mix (I use plain flour)
1 tablespoon butter, softened
Combine the brown sugar, nuts, cinnamon, and baking mix; add the butter and mix until crumbly.