Serves 4 to 6
In a saucepan, add enough water to reach two-thirds up the pan; bring to a boil. Add cornhusks and top husks with a heavy plate or bowl to keep submerged; boil for 10 minutes. Remove from heat and steep until soft and pliable, 1 to 1 1/2 hours. Drain, remove any corn silk, and pat dry before assembling tamales.
In the bowl of a food processor, process grits for 1 minute. In a small saucepan, bring stock to a low boil. Transfer grits to a bowl and add hot stock. Let stand uncovered for 10 to 12 minutes. Add masa harina and cumin, and mix until evenly combined. Cool to room temperature before proceeding.
In the bowl of an electric mixer fitted with the paddle attachment, whip lard until smooth, light, and creamy, about 2 minutes. Stir in half the masa mixture and whip until well blended. Add remaining masa mixture, little by little, until mixture resembles a thick cake batter, adding chicken stock if needed. Add baking powder and salt and whip for 1 to 2 minutes until well incorporated and smooth.
Lay 1 cornhusk on a work surface with narrow end closest to you. Top with a second cornhusk so that the fat ends are in the middle and narrow ends out. Spoon 1/4 cup masa batter into center where husks join; with the back of a spoon, spread batter into a 4-inch square. Place about 1 generous tablespoon each chicken, grated cheese, and chopped poblano in center of masa square.
Fold one side of cornhusk over filling, pulling it tight and tucking it under filling. Fold other side over filling, then top and bottom ends. With a piece of kitchen string or a thin strip of leftover cornhusk, tie tamal together loosely so that it resembles an oblong rectangular package. Repeat with remaining cornhusks and filling.
Once tamales are assembled, line a steamer basket with any remaining cornhusks and layer tamales inside steamer basket, leaving enough room for tamales to expand slightly while cooking. Cover tamales with another remaining cornhusk, cover steamer with a tight-fitting lid, and steam for 1 1/2 hours or until tender and tamales easily pull away from cornhusks. Let sit for 10 to 15 minutes before serving. Remove tamales from husks and serve with a spoon of warm salsa, garnished with crumbled queso fresco and cilantro leaves.