Step 1Bring a large covered pot of water to boil.
Step 2In a skillet large enough to hold all the ingredients, cook the onion in the olive oil over medium heat until tender, 3 to 5 minutes.
Step 3While the onion cooks, wash--but don't dry--the escarole and cut it into roughly 1-inch-wide strips, discarding the stem ends (you should have about 8 cups).
Step 4Add the minced garlic to the pan, stir and cook 1 minute, then add the escarole and a little salt. Stir then cook, covered, over medium-low heat, until tender, about 10 minutes.
Step 5Generously salt the boiling water, add the pasta and potatoes, and boil until tender, about 10 minutes. Loosely drain the pasta and potatoes and add them to the vegetables. Mix, add salt to taste, and season generously with pepper. Remove the pan from heat and stir in the cheese until melted and creamy.