Preheat oven to 350°F. Grease an 8-inch round cake pan and line the bottom with parchment paper.
In a large bowl, combine sugar, milk, eggs, oil and vanilla extract and mix to combine. Add Gluten Free Muffin Mix and mix until thoroughly combined.
Pour batter into prepared cake pan and bake until a tester inserted into the center comes out clean, about 25 - 30 minutes. Remove parchment paper and let cool completely before frosting.
Raspberry Frosting
Combine powdered sugar and soft butter and mix on low speed for 1 minute to combine with an electric mixer.
Increase speed to medium and mix until light and fluffy, 3 - 5 minutes.
Add vanilla extract, raspberries, and milk if needed to adjust consistency, and mix until raspberries have tinted the frosting pink but have not completely blended into the frosting, about 1 minute.
Slice cooled cake in half through the center, creating two equal layers. Spread an even layer of raspberry frosting on top of one layer. Place the second cake layer on top of the frosted layer and then frost the entire cake. Transfer to the refrigerator to set for 15 minutes before applying ganache.
Chocolate Ganache
Place chopped chocolate in a medium sized bowl and set aside.
Heat cream in a small saucepan to just simmering but NOT boiling. Pour hot cream over chocolate and whisk to melt chocolate and create a thick and smooth ganache.
Without letting the ganache cool, remove cake from the refrigerator and pour the very warm ganache over the top of the cake, allowing some ganache to drip down the sides of the cake. Let set for about 15 minutes then serve.
