For picky eaters, you can swap the semi-sweet chocolate chips for milk chocolate chips to make the dessert a bit sweeter and milder. If your family loves peanut butter, swirl 1/3 cup creamy peanut butter into the warm chocolate mixture before tempering the eggs. For a fun Arbor Day twist, sprinkle a handful of chopped nuts (like pecans or walnuts) over the graham crackers before pouring on the custard, to give it a little crunch that feels like a nod to the trees you’re celebrating. You can also add a teaspoon of cinnamon to the chocolate mixture for a warm, spiced flavor. If you need it a bit lighter, use 2% milk instead of whole milk, but the texture will be slightly less rich. To make cleanup easier, you can line the slow cooker with a slow-cooker liner or a sheet of parchment, but still lightly grease it so the dessert releases cleanly. For food safety, temper the eggs exactly as described so they blend smoothly into the warm chocolate without scrambling. Do not use raw, unpasteurized eggs. Make sure the dessert reaches at least 160°F in the center (you can check with an instant-read thermometer) to ensure the eggs are fully cooked. Refrigerate leftovers within 2 hours of cooking, store them covered in the fridge for up to 3 days, and reheat gently in the microwave or enjoy chilled like a soft chocolate pudding bar.