Drain your extra firm tofu by placing paper towels or cheese cloth on both sides of the tofu and placing something heavy, like a water bottle or book, over the top. After about 10 minutes, slice and cube the tofu.
Place the tofu in a large bowl and toss with 1/4 cup of corn starch. Set aside.
Place the jalapeño jelly and pineapple juice in a small sauce pan over high heat, and bring it to a boil, whisking to break up the jelly. Squeeze in about 1 tsp of lemon juice. You can add a few slices of fresh jalapeño for more spice if you like! Continue to slow boil for about 15 minutes, until reduced by half.
Heat oil in a large non-stick skillet over medium-high heat, and toss in your cornstarch coated tofu bites. Allow them to cook on each side until crispy, usually about 3-4 minutes per side. When done, remove from heat.
Once the sauce has boiled for 15 minutes, you will need to add a tiny bit of corn starch to thicken it up. Carefully spoon a few tbsp of jalapeño sauce into small bowl, then mix in 1/2 tsp of corn starch, making sure to break up any clumps. Pour it into the sauce, stir and remove from the heat.
When the tofu is done, toss it with the jalapeño jelly sauce, and garnish with sliced jalapeño and pineapple, cilantro or chives! Enjoy!