Variations: Ultimate Butter Cake or UBC and Variations; Ultimate Chocolate Butter Cake or UCBC and Variations 

A coffee cake (coffeecake) recipe variation that uses my Ultimate Butter Cake or UBC as its base.
CAKE RECIPE HELP

CINNAMON CRUNCH TOPPING 
INGREDIENTS
1/3 cup unbleached all-purpose flour, spoon into measuring cup and level to top
2/3 cup quick-cooking oatmeal
1/2 cup packed dark brown sugar
1 1/2 teaspoons ground cinnamon

5 tablespoons unsalted butter, cold
2 heaping tablespoons blueberries or any type of berries

ULTIMATE BUTTER CAKE or UBC
ONE 9 x 2-inch layer, Ultimate Butter Cake or UBC
INGREDIENTS
2 cups unbleached all purpose flour, spoon into measuring cup and level to top
1 1/2 teaspoons baking powder
1/2 teaspoon salt

3/4 cups whole or 2% milk (use cold; does not have to be at room temperature)
2 teaspoons vanilla extract with 1/4 teaspoon almond extract or 1/2 teaspoon orange or lemon extract or 2 teaspoons grated orange or 1 teaspoons lemon peel or 1/4 teaspoon citrus oil

1 cup (2 sticks / 226 grams) unsalted butter (use cold; does not have to be at room temperature )
1 cup sugar — or superfine sugar
1 1/2 large eggs* (1 large egg plus 2 tablespoons of a lightly beaten egg) — (use cold; does not have to be at room temperature )

*Question: How so I halve one large egg ?
Answer: To halve 1 large egg, whisk it in a small bowl. Let the bubbles subside. Measure 2 tablespoons. Save the rest in the refrigerator and toss later in an omelet or scrambled eggs!

INSTRUCTIONS
Topping:
1. Mix flour, quick-cooking oatmeal, packed dark brown sugar and cinnamon in a medium size mixing bowl.

2. “Cut-in” the cold butter, until the mixture resembled fine crumbs with pea-size pieces of butter remaining. (You don't want to leave large chunks of butter throughout).

3. Gingerly toss the mixture with fresh blueberries. Cover and refrigerate.

Cake:
1. Position the oven shelf in the middle of the oven. Preheat the oven to 350 degrees F.
Grease one 9- x 2-inch, preferably light colored, heavy NOT nonstick pan. (If you use dark, nonstick baking pans or ovenproof, Pyrex glass pans, be sure to reduce the oven heat by 25 degrees F).

2. In a medium bowl, whisk together the flour, baking powder, and salt; set aside. Add the vanilla to the milk and set aside.
 
3. Beat the butter in the bowl of a stand mixer, fitted with a paddle attachment, on low until softened. (If the butter is cold, it will warm quickly from the beaters – taking about 60 seconds).

4. Add the sugar in a steady stream at the side of the bowl.
Increase speed to medium and beat for 1 minute until the butter is lighter in color and aerated.

SARAH SAYS: Another way to tell when the mixture is aerated properly, is when there are ridges of butter and sugar left at the side of the bowl as the beater moves through it.
The butter is tacky and not too soft and has not melted.

5. Stop the mixer and scrape the side and bottom of the bowl with a large rubber spatula.

6. With the mixer on low, add the eggs one at a time and beat for 20 seconds after each addition.

After the eggs have been added, increase the mixer speed to medium and beat the mixture for 2 minutes. (If the eggs are cold, the batter will curdle slightly. It's ok. It will come together as the batter warms from the beaters. ) Set the kitchen timer to help you keep track of the time. The mixture will become fluffy and aerated.

SARAH SAYS: The butter is an excellent temperature. Notice that it forms ridges on the side of the mixing bowl after the beaters pull through the mixture; the batter is tacky and not too warm so it sticks to the side of the mixing bowl! The batter has become lighter in color as it takes on air bubbles and SOMEWHAT fluffy, as well!

7. With the mixer on low, add the flour mixture in 3 equal portions, alternating with the milk in 2 equal portions, beginning and ending with the flour. (If the milk is cold, the batter will curdle slightly. It's ok. It will come together when you add the flour.)

Add the flour and liquid ingredients in increments quickly; do not wait in between additions too long as you don't want to overmix the batter.

After completing the last addition of flour, stop the mixer, and scrape the side and bottom of the bowl with a large rubber spatula.
Then, let the mixer run for 30 seconds on LOW. The batter will be very thick and form ridges on the side of the bowl as the beater pulls through the batter. STOP the mixer. Do NOT overmix.

8. Remove the mixing bowl from the mixer. With a large rubber spatula, give the batter ONE or TWO quick folds to incorporate any stray flour or milk left at the sides and bottom of the bowl. Then, STOP!

Scrape the batter in the prepared baking pan and lightly smooth its top.

9. Top the Cake Batter:sprinkle the top of the Ultimate Cake batter all over with the Cinnamon Crunch topping mixture.

10. Bake the cake layer in a 350 degree preheated oven for 40 to 55 minutes or until lightly browned.
If you insert a toothpick in the middle and remove, there should be a few moist crumbs attached, but not batter.

11. Remove cakes to cool on wire racks for 10 to 15 minutes. Loosen the sides with a small metal spatula or sharp knife, taking care not to scratch the cake pan.
Invert onto cake rack and place upright to cool completely or eat slightly warm from the pan. The topping will not fall off when inverted. (The cake crumble if served when it's too hot)!

STORAGE
The cake layers store nicely. They can be stored at room temperature for about 3 or more days. The cake layers freeze well for about a month or more. Keep well wrapped.