Step 1: Prepare the Cake Batter

1. In a medium mixing bowl (2-3 quarts), use a handheld mixer on medium-low speed to combine 4 egg whites, ½ cup vegetable oil, and 1 ½ cups grape soda until well blended, about 1 minute.

2. Lower the mixer speed to low and add 15.25 oz white cake mix and 0.14 oz unsweetened grape-flavored drink mix. Mix until just incorporated and the batter is a uniform color, about 30 seconds.

3. Add 4-6 drops purple gel food coloring (adjust for desired shade) and mix until no purple streaks remain and the batter is uniformly colored, about 15-20 seconds.

   • Tip: Use room-temperature egg whites for better mixing. Mix batter gently to avoid overdeveloping gluten, ensuring a tender cake. Adjust food coloring gradually to achieve a vibrant but not overly dark purple.

Step 2: Prepare the Slow Cooker

1. Lightly grease a 4-6 quart slow cooker insert with cooking spray or a thin layer of butter to prevent sticking.

2. For easier removal, line the slow cooker with a parchment paper sling (two long strips crossed, overhanging the edges) and lightly spray the parchment.

3. Pour the batter into the slow cooker, smoothing the top with a spatula for even cooking.

   • Tip: Use a slow cooker liner or parchment sling for easy cleanup and removal. Ensure the batter is spread evenly to avoid uneven cooking.

Step 3: Slow Cook

1. Cover and cook on high for 2-3 hours or low for 4-5 hours, until a toothpick inserted in the center comes out clean or with a few moist crumbs.

2. Check doneness at the minimum time; if the center is too wet, continue cooking in 15-minute increments. If the top looks too moist, remove the lid for the last 15-20 minutes to evaporate excess moisture.

   • Tip: Place a paper towel or clean dish towel under the lid to catch condensation and prevent a soggy surface. Avoid lifting the lid too often to maintain heat. Cooking times vary by slow cooker model.

Step 4: Cool the Cake

1. Turn off the slow cooker and let the cake cool in the insert for 10-15 minutes to set slightly, making it easier to remove or scoop.

2. Use the parchment sling (if used) to lift the cake out, or scoop portions directly from the slow cooker. Transfer to a serving platter if slicing, or serve warm from the slow cooker for a rustic presentation.

   • Tip: Cool the cake slightly before frosting to prevent melting. If serving warm, scoop directly from the slow cooker for a cozy, casual vibe.

Step 5: Prepare the Buttercream Frosting

1. In a large mixing bowl (4-5 quarts) or using a stand mixer, beat 1 cup softened salted butter, 2 tsp pure vanilla extract, and ¼ tsp pure almond extract on medium-high speed for 1-1 ½ minutes, until light and fluffy.

2. Lower the mixer speed to low and add 4 cups sifted powdered sugar, 1 cup at a time, alternating with 2-3 tbsp heavy cream, until all sugar is incorporated.

3. Increase the mixer speed to medium-high and beat until the frosting is smooth and creamy, about 1 minute.

4. Add 4-6 drops purple gel food coloring and mix on medium speed until the color is uniform with no visible streaks, about 30 seconds.

   • Tip: Soften butter at room temperature for easier beating. Sift powdered sugar to avoid lumps. Adjust cream for a spreadable or pipeable consistency; add more for a thinner frosting.

Step 6: Assemble and Serve

1. Spread or pipe the purple buttercream frosting over the cooled or slightly warm cake using a spatula or a piping bag fitted with a shaped tip (e.g., open star). For piping, hold the bag ½ inch above the surface and squeeze in a spiral pattern to create a swirl effect.

2. Sprinkle purple sparkling sugar over the frosted cake for a sparkling finish.

3. Slice the cooled cake into 8-10 squares or wedges, or scoop warm portions into bowls or dessert cups (about ½ cup per serving).

4. Serve at room temperature for a classic cake texture or warm for a softer, cozy experience. Pair with milk, grape soda, or a dessert liqueur (like Crème de Violette) for a playful vibe.

   • Tip: Pipe frosting for a decorative look or spread for simplicity. Sprinkle sugar evenly for a festive sparkle. Serve in colorful bowls or plates to enhance the purple theme.