1-First Step: Preheat your oven to 350°F (175°C) and line two baking sheets with parchment paper. This prevents sticking and ensures even baking. Soften butter at room temperature for 30 minutes; avoid melting to keep dough firm.

2-Second Step: In a large bowl, cream 1 cup softened butter, 1 cup granulated sugar, and 1 cup brown sugar with an electric mixer on medium speed until light and fluffy, about 2-3 minutes. Scrape sides often for even mixing. This builds structure for thick cookies.

3-Third Step: Add 2 eggs one at a time, beating well after each. Mix in 2 tsp vanilla extract until smooth. The mixture should look glossy and pale.

4-Fourth Step: In a separate bowl, whisk 2 ¼ cups flour, 1 tsp baking soda, and ½ tsp salt. Gradually add dry mix to wet ingredients on low speed. Stop when just combined to avoid tough cookies; overmixing develops gluten.

5-Fifth Step: Gently fold in 1 ½ cups M&Ms by hand with a spatula. Reserve ¼ cup for topping. Chill dough 30-60 minutes covered; this step curbs spreading for chewy M&M cookies.

6-Sixth Step: Scoop 2-tbsp dough balls (use a cookie scoop for uniformity), place 2 inches apart on sheets. Press extra M&Ms on tops. Bake one sheet at a time in middle rack for 10-12 minutes. Edges golden, centers soft.

7-Seventh Step: Cool on sheets 5 minutes; they firm up. Transfer to wire racks. Repeat with remaining dough. Total time: 45 minutes active, yields 24.