How very sweet of you to try to reproduce the cake of your childhood for your sister. Dear Abby applauds this. She has found, she is afraid, that one can never quite do the thing. Memory adds flavor, she thinks.
However, Abby does love her coffee cake! She has much fondness for coffee and finds that a little piece of cake completes her morning repast to perfection. Henri uses the following recipe which he assures Abby is quite reliable.
Master Recipe for Quick Crumb Coffee Cake
(From "The Best Recipe" cookbook, Cook's Illustrated)
1 tablespoon dry bread crumbs
2 cups all-purpose flour
1 cup plus 2 tablespoons sugar
1 teaspoon salt
10 tablespoons (1 1/4 Sticks) unsalted butter, softened
1 teaspoon baking powder
1/2 teaspoon baking soda
3/4 cup buttermilk or low-fat (not non-fat) plain yogurt, room temperature
1 large egg, room temperature
1 teaspoon vanilla extract
3/4 cup (3 Ounces) walnuts or pecans, finely chopped
1/2 cup dark brown sugar, firmly packed
1 teaspoon ground cinnamon
Preheat oven to 350 degrees F. Generously grease bottom and lightly grease sides of 10-inch springform pan. Sprinkle bottom of pan with dry breadcrumbs, then shake lightly to coat. Tap out excess crumbs.
Whisk flour, sugar and salt in large mixing bowl until blended. Add butter and cut with whisk until mixture resembles coarse crumbs. Remove 1 cup of this mixture to separate bowl.
Whisk baking powder and soda into mixture remaining in large mixing bowl. Add buttermilk or yogurt, egg and vanilla; whisk vigorously (or beat with electric mixer at medium-high speed) until batter is thick, smooth, fluffy and frosting-like, about two minutes.
With rubber spatula, scrape batter into prepared pan and smooth the top.
Add nuts, brown sugar, and cinnamon to reserved crumbs of flour, sugar and butter; toss with a fork or your hands until blended. Sprinkle over batter, pressing lightly so that mixture adheres.
Bake cake until center is firm and cake tester comes out clean, 50 to 55 minutes. Transfer cake to rack; remove pan sides. Let cake cool completely, about 2 hours, before serving. When completely cooled, cake can be slid off pan bottom onto serving plate.