Combine milk, yeast, and sugar in a medium bowl and stir to dissolve the yeast and sugar. Let sit until foamy, about 10 minutes. Add the bacon fat and 1⁄2 teaspoon salt and whisk until smooth. Sift in the flour and stir until smooth. Cover the bowl with plastic wrap and let sit for 1 hour.
In a 10-inch skillet, cover sausages with 2 cups water over medium heat. Cover and cook 20 minutes. Transfer sausages to a cutting board and slice in half lengthwise. Keep sausages warm.
Bring a large pot of generously salted water to a boil. Add the kale and cook until wilted, about 5 minutes. Drain and roughly chop the kale. Keep kale warm.
Melt 2 tablespoons butter in a 10-inch nonstick skillet over medium-high. Add the garlic and cook 2 minutes. Add the kale and cook 2-3 minutes longer. Transfer kale to a bowl and wipe skillet clean.
Working in 8 batches, heat 1⁄2 tablespoons butter in skillet over medium-high. Add 1⁄4 cup batter to skillet and tilt the pan to evenly spread the batter. Cook until brown at the edges 2 to 3 minutes. Flip the pancake and cook 30 seconds longer. Transfer pancake to a plate and keep warm while you cook the remaining pancakes.
To serve, top each pancake with some kale, half of a sausage, and roll up.