The trick to this side dish is to avoid over-wilting the greens; a little crunchiness adds texture. Blanching the pancetta, which reduces its saltiness, is optional--to skip this step, omit salt from the recipe.
1 slice pancetta (about 1/2 in. thick; 6 oz. total), cut into 1/4-in. pieces
1/4 cup olive oil
3 shallots, quartered lengthwise
1 pkg. (8 oz.) vacuum-packed chestnuts*, halved
2 to 3 tbsp. sherry vinegar
4 heads (about 2 lbs. total) frisée, ends trimmed and leaves torn into pieces
1/2 teaspoon kosher salt
How to Make It
Bring a small saucepan of water to a boil over high heat. Cook pancetta in water 45 seconds, then drain.
Heat oil in a large, wide pot over medium heat. Add pancetta and shallots and cook, stirring occasionally, until well browned and crisp, about 10 minutes. Add chestnuts and cook until they start to brown, about 3 minutes more.
Add vinegar, frisée, and salt, stirring to coat with oil. Remove from heat and immediately transfer to a serving bowl.