Add cream and 4 tablespoons sugar to clean FourSide or WildSide jar. Secure lid and blend on "Speed 1" for 30 seconds or until cream solidifies. Add berries and secure lid. Blend on "Speed 1" for 20 seconds or until berries are incorporated. Refrigerate berry-infused buttercream for at least 1 hour.
Add eggs, milk, oil, and vanilla to FourSide or WildSide jar. Secure lid and select "Batter." Remove lid and add 2 tablespoons sugar, salt, baking powder, and flour to jar. Secure lid, and press "Pulse" 4–6 times to incorporate ingredients; do not overblend. Allow batter to rest for 5 minutes.
Meanwhile, heat greased waffle iron to medium-high heat. Pour appropriate amount of batter onto greased waffle iron, and cook until golden brown. Repeat with remaining batter. Top waffles with berry-infused buttercream, and then serve.