1. In a large pot, bring water to a boil over medium-high. Gradually add chard and cook until it is just wilted, 2 to 3 minutes. Transfer to a colander to drain, pressing out as much liquid as possible.

2. In pot, melt butter. Whisking constantly, add flour and cook 1 minute. Whisking constantly, slowly add milk. Cook, whisking along bottom of pot, until mixture comes to a boil and thickens, 2 to 3 minutes. Add chard and stir until coated. Stir in nutmeg and season with salt and pepper.