Combine first 3 ingredients; stir in pecans and butter until crumbly.
Banana-Sour Cream Coffee Cake: Prepare batter as directed, reducing sour cream to 1/2 cup and adding 1 cup mashed ripe banana. Sprinkle 1 cup toffee bits evenly over top of batter; sprinkle with Streusel Topping, and bake 30 minutes. Prep: 25 min., Bake: 30 min.
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