Streusel-filled Coffee Cake

This is another recipe from the Betty Crocker Picture Cookbook circa 1961.  

3/4 cup sugar
1/4 cup soft shortening
1 egg
1/2 cup milk
1 1/2 cups flour
2 teaspoons baking powder
1/2 teaspoon salt

Streusel Mixture
1/2 cup brown sugar (packed)
2 tablespoons flour
2 teaspoons cinnamon
2 tablespoons butter
1/2 cup chopped nuts (optional)

Heat oven to 375 degrees.  Grease and flour a 9x9 square pan.  Mix sugar, shortening and egg thoroughly.  Stir in milk. Blend dry ingredients; stir in.  Spread 1/2 batter in pan.

Mix streusel mixture and spread 1/2 on first layer of batter in pan.
Add the remaining batter and sprinkle remaining streusel over top.

​Bake 25-35 minutes, or until toothpick stuck into center comes out clean.  Serve warm.