Swiss Chard with Horseradish

Ingredients

• 1.5 tablespoons horseradish white drained to taste (not )
• 3 tablespoons olive oil 
• 1 medium onion halved lengthwise thinly sliced
• 0.5 teaspoon salt 
• 3 pounds swiss chard green (2 to 3 bunches; see Cooks' notes)
• 3 tablespoons water 

Equipment

• bowl
• paper towels
• pot
• ziploc bags
• tongs
• colander

Directions

1. Cut out stems and center ribs from chard, discarding any tough parts (see Cooks' notes), then chop. Wash leaves well, then cut in half crosswise (leave whole if on the smaller side).
2. Heat oil in a wide heavy pot (5- to 7-quart capacity) over medium heat until shimmering, then cook onion, stirring occasionally, until it begins to soften, about 5 minutes.
3. Add chard stems and ribs, the water, and 1/2 teaspoon salt, and cook, covered, until just tender, 8 to 10 minutes.
4. Increase heat to medium-high.
5. Add leaves in handfuls, turning with tongs and adding more as previous batches wilt, until all leaves have been added to pot. Cover with lid, then reduce heat to medium and cook, stirring once or twice, until just tender (do not overcook), 2 to 3 minutes.
6. Remove from heat and stir in horseradish.
7. •Chard tends to be quite sandy, so you will likely need to wash it in several changes of cold water in a large, deep bowl or clean sink. If cooking right away, just drain it in a colander, but don't spin it dry.•Raw chard can be sliced and chopped 1 day ahead; keep leaves and ribs in separate resealable plastic bags. If it is still wet from washing, spin it dry and stick a paper towel in each bag (wet greens in plastic bags deteriorate quickly). When cooking, you'll likely need to add a little more water to make up for the water not still clinging to the leaves.•Green Swiss chard has wider stems than red or rainbow chard. Bunches vary in how much of the stem is attached, so the amount of pale stems and green leaves you end up with in 3 pounds will vary.