Preheat the oven. Preheat your oven to 400°F and position the rack in the center. Then, line a muffin tin with cupcake liners (parchment or silicone liners work well).
Mix the wet ingredients. In a medium bowl, combine the wet ingredients: 1/3 cup vegetable oil (or melted butter), 1 egg, and 1/3 cup milk. Whisk together until well combined.
Whisk the dry ingredients. Whisk together the dry ingredients in a separate large bowl: 1 1/2 cups all-purpose flour, 3/4 cup white sugar, 2 teaspoons baking powder, and 1/2 teaspoon salt. Make sure everything is evenly mixed.
Combine the wet and dry ingredients. Pour the wet ingredients into the bowl with the dry ingredients. Gently stir the mixture until just combined—be careful not to overmix. The batter should still be slightly lumpy. Fold in 1 cup of chocolate chips.
Fill the muffin tins. Scoop the batter into the prepared muffin tins, filling each cup about 3/4 full. This recipe makes 6 jumbo muffins or 12 regular-sized muffins. For a sweet, crunchy top, sprinkle a little extra sugar over each muffin.
Bake the muffins. Bake in the preheated oven for 25-30 minutes for jumbo muffins (or 20-25 minutes for regular-sized muffins). The muffins are done when a toothpick inserted into the center comes out clean or with just a few crumbs attached.
Cool and serve. Remove the muffins from the oven and allow them to cool in the tin for 5 minutes. Then, transfer them to a wire rack to cool completely. Enjoy your muffins warm or at room temperature. They’ll stay fresh for a day at room temperature or can be frozen once fully cooled.