In a mixing bowl, beat together softened butter at room temperature and sugar. Use an electric hand mixer on a medium-speed setting and beat until the butter mixture is fluffy.
Add the canola oil and beat for another minute.
Sift together the flour, baking powder, and salt. Then add these dry ingredients to the butter, sugar, and oil mixture. Add the mixed nuts and use a spatula to mix everything.
Combine the crumbly cookie dough using your hands.
Begin adding a little of the warm milk (gradually as needed) or warm water to knead the dough. Make a firm ball of dough. If it’s still too crumbly, add another tablespoon of milk and combine.
Use a cookie scoop or your hands to make small balls of the cookie dough. Place the balls on a greased cookie sheet (or line it with parchment paper). Put enough space between the balls so they can expand while baking.
Press the balls gently with a fork or your thumb. Don’t press too hard, or they may split.
Bake for 15 minutes in the preheated oven. Keep the baked cookies on the baking sheet until they completely cool down.
Keep an eye on the cookies towards the end of baking and remove them from the oven when they get to a light golden brown color.