How to make muffins:
1. Line the pan(s) with paper or foil liners; coat the liners with cooking spray. (For savory muffins, dust with flour after spraying.)
2. Fill each liner 2/3 to 3/4 full with batter and bake at 350 degrees F until a toothpick comes out clean.
1. Streusel: Make the topping: Mix 2/3 cup each chopped pecans, brown sugar and flour, and 1/4 teaspoon salt; work in 5 tablespoons cold cubed butter. Make the batter: Mix 2 cups flour, 1 teaspoon baking powder, 1/2 teaspoon each cinnamon and salt, and 1/4 teaspoon baking soda. Whisk 3 eggs, 3/4 cup sugar, 1 stick melted butter, 1 cup sour cream and 1 teaspoon vanilla; fold into the flour mixture. Divide among 12 prepared muffin cups, sprinkle with the topping and bake 20 to 25 minutes.
2. Earl Grey: Make Streusel Muffins (No. 1), replacing the pecans with oats, reducing the sour cream to 3/4 cup and adding 1/3 cup strong Earl Grey tea with the vanilla.
3. Coffee Cake: Make Streusel Muffins (No. 1), doubling the topping; divide among 18 prepared muffin cups and bake.
4. Snickerdoodle: Make cinnamon crumble: Mix 2/3 cup sugar, 1/3 cup flour and 1 tablespoon cinnamon; mash in 1/2 stick softened butter. Make the batter for Streusel Muffins (No. 1). Stir 1/2 cup of the cinnamon crumble into the batter; divide among 12 prepared muffin cups and top with the remaining crumble. Bake 25 to 28 minutes.
5. Ginger-Lemon Minis: Make Gingerbread Muffins (No. 6), dividing the batter among 36 to 48 prepared mini muffin cups. Bake 16 to 18 minutes. Make a dent in each muffin while still warm; cool. Fill with jarred lemon curd.
6. Gingerbread: Mix 2 cups flour, 2 tablespoons cocoa powder, 1 tablespoon ground ginger, 1 teaspoon baking soda and 1/2 teaspoon salt. Whisk 1 stick melted butter, 1/2 cup each sugar and molasses, 1/4 cup milk and 2 eggs; fold into the flour mixture. Divide among 12 prepared muffin cups; bake 20 to 25 minutes.
7. Ginger-Fig: Make Gingerbread Muffins (No. 6), adding 1/4 cup finely chopped dried figs and 1/4 teaspoon orange zest with the eggs.
8. Sugar-and-Spice Minis: Make Gingerbread Muffins (No. 6), adding 1/2 teaspoon pepper with the flour and 1 tablespoon finely grated ginger with the eggs. Divide among 36 to 48 prepared mini muffin cups and sprinkle with chopped crystallized ginger. Bake 16 to 18 minutes.
9. Banana: Mix 2 cups flour, 1/2 cup chopped nuts, 1 teaspoon baking powder, 1/2 teaspoon salt and 1/4 teaspoon baking soda. Whisk 3/4 cup brown sugar, 1 stick melted butter, 1/2 cup each mashed banana and sour cream, and 2 eggs; fold into the flour mixture. Divide among 12 prepared muffin cups; bake 20 to 25 minutes.
10. Apple-Cranberry: Make Banana Muffins (No. 9), adding 1/2 teaspoon cinnamon with the flour and replacing the nuts with dried cranberries and the banana with applesauce. Top with dried apples and dried cranberries before baking.