Preheat the Oven: Begin by preheating your oven to 350°F (175°C). Grease your cake pan and line the bottom with parchment paper for easy removal of the cake.

Prepare the Oats: Place the oats in a mixing bowl and pour the boiling water over them. Let the oats sit for about 5 minutes to soften and absorb the water.

Cream the Butter and Sugar: In a separate bowl, cream together the softened butter and granulated sugar until light and fluffy. This should take about 2-3 minutes.

Add Eggs and Vanilla: Beat in the eggs, one at a time, ensuring each is fully incorporated before adding the next. Stir in the vanilla extract.

Combine Dry Ingredients: In another bowl, sift together the flour, cocoa powder, baking powder, baking soda, and salt.

Mix Wet and Dry Ingredients: Gradually add the dry ingredients to the butter and sugar mixture, mixing just until combined. Gently fold in the softened oats.

Add Optional Ingredients: If desired, fold in the mini chocolate chips and chopped nuts for added flavor and texture.

Bake the Cake: Pour the batter into the prepared cake pan, spreading it evenly. Bake in the preheated oven for 35-40 minutes, or until a toothpick inserted into the center comes out clean.

Cool and Serve: Allow the cake to cool in the pan for about 10 minutes before transferring it to a wire rack to cool completely. Once cooled, cut into slices and serve.