Cut off 1/4 inch of the top of the pepper if using a pepper roaster; if not cut them lengthwise. Remove the seeds and ribs.
Heat oil on MED HIGH. Once heated, cook onions until soft. Season with chili powder, salt and pepper. Add garlic and chorizo. Cook until the sausage is done (should be 9 mins). Put it on a plate to cool down (use a paper towel to absorb fat if you like).
Blend the onion/sausage with softened cream cheese and cheese. Stuff the peppers with your hands. Put the peppers in the roaster orput them on a foil lined roasting tray.
Sprinkle cajun seasoning over stuffed peppers.
You can cook them on the grill or in the over. Oven: preheat to 400 degrees, cook until soft/tender (25 mins). Grill: roast over MED HIGH heat.
Most cooks ruin stuffed jalapeños by overfilling the pepper cavities, which causes the cheese and meat mixture to expand, boil over, and empty entirely onto the pan during the baking process. Preventing this structural failure requires understanding how fat behaves under high heat. When chorizo and cream cheese undergo sustained baking at 400 degrees Fahrenheit, the lipids liquefy rapidly before the pepper softens. Packing the cavity too tightly leaves no room for that expanding fat, forcing the filling out through the top opening. Instead, fill each pepper only until the mixture is flush with the cut edges, allowing internal room for thermal expansion without overflow. Scaling this recipe up or down introduces distinct mathematical adjustments for the filling components. Because whole jalapeños vary unpredictably in internal volume, scaling the meat and cheese proportionally often leaves an excess of filling. A reliable ratio for stuffing requires roughly one ounce of combined meat and cheese per large pepper, meaning a batch of 18 peppers needs about one pound of chorizo and four ounces of cheddar. When halving the recipe, keep the ratio of soft cream cheese to hard cheddar at one tablespoon to two ounces per half-pound of sausage to maintain structural binding. Without enough softened cream cheese acting as an emulsion anchor, the melted cheddar separates from the meat and pools into grease. Cook the filling mixture for precisely nine minutes on medium-high heat initially, ensuring the onions soften without burning the minced garlic. Cool the cooked sausage completely on paper towels before mixing in the cheeses; hot meat will cause the cream cheese to break prematurely and release its moisture into the blend. Bake the assembled peppers for 25 minutes until the skins blister and soften completely, or transfer them to a medium-high grill for direct roasting.