Measure and melt the 3 tablespoons butter. Reserve 1 tablespoon of the melted butter for cooking; set it aside. Use the remaining 2 tablespoons in the batter.
In a blender, combine 1 1/4 cups milk, 1/4 cup heavy cream, 1 cup all-purpose flour, 4 large eggs, 1 tablespoon sugar, 2 tablespoons melted butter, and 1/4 teaspoon salt. Blend until the batter is smooth and fully combined.
Let the batter rest for 15 minutes at room temperature (or transfer to an airtight container and refrigerate for up to 1 day). Stir the batter before cooking.
Heat a 10–12 inch nonstick skillet over medium heat. Lightly coat the skillet with the 1 tablespoon reserved melted butter (use a pastry brush or a folded paper towel to spread a thin layer).
Pour 1/3 cup of batter into the hot skillet, immediately tilting and swirling the pan so the batter forms a thin, even layer.
Cook until the edges are slightly crisp and the center is set, about 30 to 45 seconds. Using a thin spatula, carefully lift an edge and flip the crepe. Cook the other side for 20 to 30 seconds. Slide the cooked crepe onto a plate and keep warm. Repeat with the remaining batter, re-coating the skillet lightly with the reserved butter as needed.
In a medium bowl, whisk together 1 package (3.4 oz) instant vanilla pudding mix and 1 cup cold milk until the mixture is slightly thickened and smooth.
Fold 8 oz thawed frozen whipped topping into the pudding mixture until completely combined to make the cream filling.
For the chocolate ganache: heat 1 cup heavy cream in the microwave or on the stovetop until hot but not boiling. Pour the hot cream over 8 oz semi-sweet chocolate chips in a heatproof bowl. Let sit for 20 seconds, then stir until the chocolate is completely melted and the ganache is smooth.
To assemble, place about 1/3 cup (or more if desired) of the cream filling in the center of each crepe. Roll or fold each crepe to enclose the filling.
Drizzle the top of each filled crepe with the chocolate ganache. Serve immediately.