Ingredients

• 3/4 cup butter, softened
• 1 cup sugar
• 3/4 cup milk
• 1 egg
• 1 3/4 cup flour
• 2 1/2 tbs baking powder
• 1/2 tsp salt
• 1 tsp cinnamon
• 1 cup apples (peeled & cored), chopped to roughly 1/4in pieces
• 1 tbs flour

Streusel Topping:

• 2 tbs butter
• 1/4 cup brown sugar
• 1/4 cup flour
• 1 tsp cinnamon

Directions

• Preheat oven to 375F.
• Cream butter and sugar. I know a lot of recipes call for creaming butter and sugar and you can sometimes just wing it without doing this step, but this is one of those recipes where if you don’t cream the butter and sugar they really don’t turn out right. Trust me on this one. The order of steps matters.
• Add milk & egg; beat until smooth.
• Add first measure of flour, baking powder, cinnamon, and salt; mix until moistened
• Toss apple chunks in 1tbs flour. Add to batter and fold in (but just like with berries, no more than three turns!).
• Fill muffin cups 1/2-3/4 full.
• Mix the ingredients for the topping with your fingers to roughly the consistency of wet sand. 
• Sprinkle streusel topping onto batter in cups.
• Bake for 25 minutes.

(my own recipe)